Latest Group Publications

Our large and diverse group are busy in a wide array of research. Please scroll down to see the latest publications.

Gravitationally induced decoherence vs space-time diffusion: testing the quantum nature of gravity

We consider two interacting systems when one is treated classically while the other system remains quantum. Consistent dynamics of this coupling has been shown to exist, and explored in the context of treating space-time classically. Here, we prove that any such hybrid dynamics necessarily results in decoherence of the quantum system, and a breakdown in predictability in the classical phase space. We further prove that a trade-off between the rate of this decoherence and the degree of diffusion induced in the classical system is a general feature of all classical quantum dynamics; long coherence times require strong diffusion in phase-space relative to the strength of the coupling. Applying the trade-off relation to gravity, we find a relationship between the strength of gravitationally-induced decoherence versus diffusion of the metric and its conjugate momenta. This provides an experimental signature of theories in which gravity is fundamentally classical. Bounds on decoherence rates arising from current interferometry experiments, combined with precision measurements of mass, place significant restrictions on theories where Einstein's classical theory of gravity interacts with quantum matter. We find that part of the parameter space of such theories are already squeezed out, and provide figures of merit which can be used in future mass measurements and interference experiments.

December 2023: Oppenheim, J; Sparaciari, C; Soda, B; Weller-Davies, Z (Nature Communications)

Planetesimals at DZ stars - I. Chondritic compositions and a massive accretion event

There is a wealth of evidence to suggest that planetary systems can survive beyond the main sequence. Most commonly, white dwarfs are found to be accreting material from tidally disrupted asteroids, whose bulk compositions are reflected by the metals polluting the stellar photospheres. While many examples are known, most lack the deep, high-resolution data required to detect multiple elements, and thus characterize the planetesimals that orbit them. Here, spectra of seven DZ white dwarfs observed with Keck High Resolution Echelle Spectrometer (HIRES) are analysed, where up to nine metals are measured per star. Their compositions are compared against those of Solar system objects, working in a Bayesian framework to infer or marginalize over the accretion history. All of the stars have been accreting primitive material, similar to chondrites, with hints of a Mercury-like composition at one star. The most polluted star is observed several Myr after its last major accretion episode, in which a Moon-sized object met its demise.

December 2023: Swan, A; Farihi, J; Melis, C; Dufour, P; Desch, S; et al. (Monthly Notices of the Royal Astronomical Society)

JWST observations of the Ring Nebula (NGC 6720): I. Imaging of the rings, globules, and arcs

We present JWST images of the well-known planetary nebula NGC 6720 (the Ring Nebula), covering wavelengths from 1.6$\, \mu$m to 25 $\, \mu$m. The bright shell is strongly fragmented with some 20 000 dense globules, bright in H₂, with a characteristic diameter of 0.2 arcsec and density n_H ~ 10⁵-10⁶ cm^-3. The shell contains a narrow ring of polycyclic aromatic hydrocarbon (PAH) emission. H₂ is found throughout the shell and also in the halo. H₂ in the halo may be located on the swept-up walls of a biconal polar flow. The central cavity is filled with high ionization gas and shows two linear structures which we suggest are the edges of a biconal flow, seen in projection against the cavity. The central star is located 2 arcsec from the emission centroid of the cavity and shell. Linear features ('spikes') extend outward from the ring, pointing away from the central star. Hydrodynamical simulations reproduce the clumping and possibly the spikes. Around ten low-contrast, regularly spaced concentric arc-like features are present; they suggest orbital modulation by a low-mass companion with a period of about 280 yr. A previously known much wider companion is located at a projected separation of about 15 000 au; we show that it is an M2-M4 dwarf. NGC 6720 is therefore a triple star system. These features, including the multiplicity, are similar to those seen in the Southern Ring Nebula (NGC 3132) and may be a common aspect of such nebulae.

December 2023: Wesson, R; Matsuura, M; Zijlstra, A; Volk, K; Kavanagh, P; et al. (Monthly Notices of the Royal Astronomical Society)

De-noising of galaxy optical spectra with autoencoders

Optical spectra contain a wealth of information about the physical properties and formation histories of galaxies. Often though, spectra are too noisy for this information to be accurately retrieved. In this study, we explore how machine learning methods can be used to de-noise spectra and increase the amount of information we can gain without having to turn to sample averaging methods such as spectral stacking. Using machine learning methods trained on noise-added spectra - Sloan Digital Sky Survey (SDSS) spectra with Gaussian noise added - we investigate methods of maximizing the information we can gain from these spectra, in particular from emission lines, such that more detailed analysis can be performed. We produce a variational autoencoder (VAE) model, and apply it on a sample of noise-added spectra. Compared to the flux measured in the original SDSS spectra, the model values are accurate within 0.3-0.5 dex, depending on the specific spectral line and signal-to-noise ratio. Overall, the VAE performs better than a principal component analysis method, in terms of reconstruction loss and accuracy of the recovered line fluxes. To demonstrate the applicability and usefulness of the method in the context of large optical spectroscopy surveys, we simulate a population of spectra with noise similar to that in galaxies at z = 0.1 observed by the Dark Energy Spectroscopic Instrument (DESI). We show that we can recover the shape and scatter of the mass-metallicity relation in this 'DESI-like' sample, in a way that is not possible without the VAE-assisted de-noising.

December 2023: Scourfield, M; Saintonge, A; de Mijolla, D; Viti, S (Monthly Notices of the Royal Astronomical Society)

Rediscovering orbital mechanics with machine learning

We present an approach for using machine learning to automatically discover the governing equations and unknown properties (in this case, masses) of real physical systems from observations. We train a 'graph neural network' to simulate the dynamics of our Solar System's Sun, planets, and large moons from 30 years of trajectory data. We then use symbolic regression to correctly infer an analytical expression for the force law implicitly learned by the neural network, which our results showed is equivalent to Newton's law of gravitation. The key assumptions our method makes are translational and rotational equivariance, and Newton's second and third laws of motion. It did not, however, require any assumptions about the masses of planets and moons or physical constants, but nonetheless, they, too, were accurately inferred with our method. Naturally, the classical law of gravitation has been known since Isaac Newton, but our results demonstrate that our method can discover unknown laws and hidden properties from observed data.

December 2023: Lemos, P; Jeffrey, N; Cranmer, M; Ho, S; Battaglia, P (Machine Learning: Science and Technology)

YunMa: Enabling Spectral Retrievals of Exoplanetary Clouds

In this paper, we present YunMa, an exoplanet cloud simulation and retrieval package, which enables the study of cloud microphysics and radiative properties in exoplanetary atmospheres. YunMa simulates the vertical distribution and sizes of cloud particles and their corresponding scattering signature in transit spectra. We validated YunMa against results from the literature. When coupled to the TauREx 3 platform, an open Bayesian framework for spectral retrievals, YunMa enables the retrieval of the cloud properties and parameters from transit spectra of exoplanets. The sedimentation efficiency (f _sed), which controls the cloud microphysics, is set as a free parameter in retrievals. We assess the retrieval performances of YunMa through 28 instances of a K2-18 b-like atmosphere with different fractions of H₂/He and N₂, and assuming water clouds. Our results show a substantial improvement in retrieval performances when using YunMa instead of a simple opaque cloud model and highlight the need to include cloud radiative transfer and microphysics to interpret the next-generation data for exoplanet atmospheres. This work also inspires instrumental development for future flagships by demonstrating retrieval performances with different data quality.

November 2023: Ma, S; Ito, Y; Al-Refaie, A; Changeat, Q; Edwards, B; et al. (The Astrophysical Journal)

Understanding molecular abundances in star-forming regions using interpretable machine learning

Astrochemical modelling of the interstellar medium typically makes use of complex computational codes with parameters whose values can be varied. It is not always clear what the exact nature of the relationship is between these input parameters and the output molecular abundances. In this work, a feature importance analysis is conducted using SHapley Additive exPlanations (SHAP), an interpretable machine learning technique, to identify the most important physical parameters as well as their relationship with each output. The outputs are the abundances of species and ratios of abundances. In order to reduce the time taken for this process, a neural network emulator is trained to model each species' output abundance and this emulator is used to perform the interpretable machine learning. SHAP is then used to further explore the relationship between the physical features and the abundances for the various species and ratios we considered. H₂O and CO's gas phase abundances are found to strongly depend on the metallicity. NH₃ has a strong temperature dependence, with there being two temperature regimes (<100 K and >100 K). By analysing the chemical network, we relate this to the chemical reactions in our network and find the increased temperature results in increased efficiency of destruction pathways. We investigate the HCN/HNC ratio and show that it can be used as a cosmic thermometer, agreeing with the literature. This ratio is also found to be correlated with the metallicity. The HCN/CS ratio serves as a density tracer, but also has three separate temperature-dependence regimes, which are linked to the chemistry of the two molecules.

November 2023: Heyl, J; Butterworth, J; Viti, S (Monthly Notices of the Royal Astronomical Society)

Evidence for late-time dust formation in the ejecta of supernova SN 1995N from emission-line asymmetries

We present a study of the dust associated with the core-collapse supernova SN 1995N. Infrared emission detected 14-15 yr after the explosion was previously attributed to thermally echoing circumstellar material (CSM) associated with the supernova (SN) progenitor. We argue that this late-time emission is unlikely to be an echo, and is more plausibly explained by newly formed dust in the SN ejecta, indirectly heated by the interaction between the ejecta and the CSM. Further evidence in support of this scenario comes from emission-line profiles in spectra obtained 22 yr after the explosion; these are asymmetric, showing greater attenuation on the red wing, consistent with absorption by dust within the expanding ejecta. The spectral energy distribution and emission-line profiles at epochs later than ~5000 d are both consistent with the presence of about 0.4 M_⊙ of amorphous carbon dust. The onset of dust formation is apparent in archival optical spectra, taken between 700 and 1700 d after the assumed explosion date. As this is considerably later than most other instances where the onset of dust formation has been detected, we argue that the explosion date must be later than previously assumed.

November 2023: Wesson, R; Bevan, A; Barlow, M; De Looze, I; Matsuura, M; et al. (Monthly Notices of the Royal Astronomical Society)

Exploring the Ability of Hubble Space Telescope WFC3 G141 to Uncover Trends in Populations of Exoplanet Atmospheres through a Homogeneous Transmission Survey of 70 Gaseous Planets

We present analysis of the atmospheres of 70 gaseous extrasolar planets via transit spectroscopy with Hubble's Wide Field Camera 3 (WFC3). For over half of these, we statistically detect spectral modulation that our retrievals attribute to molecular species. Among these, we use Bayesian hierarchical modeling to search for chemical trends with bulk parameters. We use the extracted water abundance to infer the atmospheric metallicity and compare it to the planet's mass. We also run chemical equilibrium retrievals, fitting for the atmospheric metallicity directly. However, although previous studies have found evidence of a mass-metallicity trend, we find no such relation within our data. For the hotter planets within our sample, we find evidence for thermal dissociation of dihydrogen and water via the H^- opacity. We suggest that the general lack of trends seen across this population study could be due to (i) the insufficient spectral coverage offered by the Hubble Space Telescope's WFC3 G141 band, (ii) the lack of a simple trend across the whole population, (iii) the essentially random nature of the target selection for this study, or (iv) a combination of all the above. We set out how we can learn from this vast data set going forward in an attempt to ensure comparative planetology can be undertaken in the future with facilities such as the JWST, Twinkle, and Ariel. We conclude that a wider simultaneous spectral coverage is required as well as a more structured approach to target selection.

November 2023: Edwards, B; Changeat, Q; Tsiaras, A; Yip, K; Al-Refaie, A; et al. (The Astrophysical Journal Supplement Series)

New atomic data for C I Rydberg states compared with solar UV spectra

We use the Breit-Pauli R-matrix method to calculate accurate energies and radiative data for states in C I up to n = 30 and with l ≤ 3. We provide the full data set of decays to the five 2s² 2p² ground configuration states ³P_0,1,2, ¹D₂, and ¹S₀. This is the first complete set of data for transitions from n ≥ 5. We compare oscillator strengths and transition probabilities with the few previously calculated values for such transitions, finding generally good agreement (within 10 per cent) with the exception of values recently recommended by National Institute of Standards and Technology, where significant discrepancies are found. We then calculate spectral line intensities originating from the Rydberg states using typical chromospheric conditions and assuming local thermal equilibrium, and compare them with well-calibrated Solar and Heliospheric Observatory Solar Ultraviolet Measurements of Emitted Radiation ultraviolet (UV) spectra of the quiet Sun. The relative intensities of the Rydberg series are in excellent agreement with observation, which provides firm evidence for the identifications and blends of nearly 200 UV lines. Such comparison also resulted in a large number of new identifications of C I lines in the spectra. We also estimate optical depth effects and find that these can account for much of the absorption noted in the observations. The atomic data can be applied to model a wide range of solar and astrophysical observations.

November 2023: Storey, P; Dufresne, R; Del Zanna, G (Monthly Notices of the Royal Astronomical Society)

ExoMol line lists - LIII: Empirical Rovibronic spectra Yttrium Oxide (YO)

Empirical line lists BRYTS for the open shell molecule ⁸⁹Y¹⁶O (yttrium oxide) and its isotopologues are presented. The line list covers the 6 lowest electronic states: X ²Σ⁺, A ²Π, A' ²Δ, B ²Σ⁺, C ²Π and D ²Σ⁺ up to 60 000 cm^-1 (<0.167 μm) for rotational excitation up to J = 400.5. An ab initio spectroscopic model consisting of potential energy curves (PECs), spin-orbit and electronic angular momentum couplings is refined by fitting to experimentally determined energies of YO, derived from published YO experimental transition frequency data. The model is complemented by empirical spin-rotation and Λ-doubling curves and ab initio dipole moment and transition dipole moment curves computed using MRCI. The ab initio PECs computed using the complete basis set limit extrapolation and the CCSD(T) method with its higher quality provide an excellent initial approximation for the refinement. Non-adiabatic coupling curves for two pairs of states of the same symmetry A/C and B/D are computed using a state-averaged CASSCF and used to build diabatic representations for the A ²Π, C ²Π, B ²Σ⁺ and D ²Σ⁺ curves. The experimentally derived energies of ⁸⁹Y¹⁶O utilised in the fit are used to replace the corresponding calculated energy values in the BRYTS line list. Simulated spectra of YO show excellent agreement with the experiment, where it is available. Calculated lifetimes of YO are tuned to agree well with the experiment, where available. The BRYTS YO line lists are available from the ExoMol database (www.exomol.com).

October 2023: Yurchenko, S; Brady, R; Tennyson, J; Smirnov, A; Vasilyev, O; et al. (Monthly Notices of the Royal Astronomical Society)

Discovery of dipolar chromospheres in two white dwarfs

This paper reports the ULTRACAM discovery of dipolar surface spots in two cool magnetic white dwarfs with Balmer emission lines, while a third system exhibits a single spot, similar to the prototype GD 356. The light curves are modelled with simple, circular, isothermal dark spots, yielding relatively large regions with minimum angular radii of 20°. For those stars with two light-curve minima, the dual spots are likely observed at high inclination (or colatitude); however, identical and antipodal spots cannot simultaneously reproduce both the distinct minima depths and the phases of the light-curve maxima. The amplitudes of the multiband photometric variability reported here are all several times larger than that observed in the prototype GD 356; nevertheless, all DAHe stars with available data appear to have light-curve amplitudes that increase towards the blue in correlated ratios. This behaviour is consistent with cool spots that produce higher contrasts at shorter wavelengths, with remarkably similar spectral properties given the diversity of magnetic field strengths and rotation rates. These findings support the interpretation that some magnetic white dwarfs generate intrinsic chromospheres as they cool, and that no external source is responsible for the observed temperature inversion. Spectroscopic time-series data for DAHe stars is paramount for further characterization, where it is important to obtain well-sampled data, and consider wavelength shifts, equivalent widths, and spectropolarimetry.

October 2023: Farihi, J; Hermes, J; Littlefair, S; Howarth, I; Walters, N; et al. (Monthly Notices of the Royal Astronomical Society)

JADES: Discovery of extremely high equivalent width Lyman-α emission from a faint galaxy within an ionized bubble at z = 7.3

We report the discovery of a remarkable Lyα emitting galaxy at z = 7.2782, JADES-GS+53.16746−27.7720 (shortened to JADES-GS-z7-LA), with rest-frame equivalent width, EW₀(Lyα) = 388.0 ± 88.8 Å and UV magnitude −17.0. The spectroscopic redshift is confirmed via rest-frame optical lines [O II], Hβ and [O III] in its JWST/NIRSpec Micro-Shutter Assembly (MSA) spectrum. The Lyα line is detected in both lower resolution (R ∼ 100) PRISM as well as medium resolution (R ∼ 1000) G140M grating spectra. The line spread function-deconvolved Lyα full width at half maximum in the grating is 383.9 ± 56.2 km s⁻¹ and the Lyα velocity offset compared to the systemic redshift is 113.3 ± 80.0 km s⁻¹, indicative of very little neutral gas or dust within the galaxy. We estimate the Lyα escape fraction to be > 70%. JADES-GS-z7-LA has a [O III]/[O II] ratio (O32) of 11.1 ± 2.2 and a ([O III] + [O II])/Hβ ratio (R23) of 11.2 ± 2.6, consistent with low metallicity and high ionization parameters. Deep NIRCam imaging also revealed a close companion source (separated by 0.23″), which exhibits similar photometry to that of JADES-GS-z7-LA, with a photometric excess in the F410M NIRCam image consistent with [O III] + Hβ emission at the same redshift. The spectral energy distribution of JADES-GS-z7-LA indicates a "bursty" star formation history, with a low stellar mass of ≈10⁷ M_⊙. Assuming that the Lyα transmission through the intergalactic medium is the same as its measured escape fraction, an ionized region of size > 1.5 pMpc is needed to explain the high Lyα EW and low velocity offset compared to systemic seen in JADES-GS-z7-LA. Owing to its UV-faintness, we show that it is incapable of single-handedly ionizing a region large enough to explain its Lyα emission. Therefore, we suggest that JADES-GS-z7-LA (and possibly the companion source) may be a part of a larger overdensity, presenting direct evidence of overlapping ionized bubbles at z > 7.

October 2023: Saxena, A; Robertson, B; Bunker, A; Endsley, R; Cameron, A; et al. (Astronomy and Astrophysics)

A simulation-based inference pipeline for cosmic shear with the Kilo-Degree Survey

The standard approach to inference from cosmic large-scale structure data employs summary statistics that are compared to analytic models in a Gaussian likelihood with pre-computed covariance. To overcome the idealizing assumptions about the form of the likelihood and the complexity of the data inherent to the standard approach, we investigate simulation-based inference (SBI), which learns the likelihood as a probability density parameterized by a neural network. We construct suites of simulated summary statistics, exactly Gaussian distributed for validation purposes, for the most recent Kilo-Degree Survey (KiDS) weak gravitational lensing analysis and demonstrate that SBI recovers the full 12-dimensional KiDS posterior distribution with just under 10⁴ simulations. We optimize the simulation strategy by initially covering the parameter space by a hypercube, followed by batches of actively learnt additional points. The data compression in our SBI implementation is robust to suboptimal choices of fiducial parameter values and of data covariance. Together with a fast simulator, SBI is therefore a competitive and more versatile alternative to standard inference.

October 2023: Lin, K; von wietersheim-Kramsta, M; Joachimi, B; Feeney, S (Monthly Notices of the Royal Astronomical Society)

Measurement of stellar and substellar winds using white dwarf hosts

White dwarfs stars are known to be polluted by their active planetary systems, but little attention has been paid to the accretion of wind from low-mass companions. The capture of stellar or substellar wind by white dwarfs is one of few methods available to astronomers which can assess mass-loss rates from unevolved stars and brown dwarfs, and the only known method to extract their chemical compositions. In this work, four white dwarfs with closely orbiting, L-type brown dwarf companions are studied to place limits on the accretion of a substellar wind, with one case of a detection, and at an extremely non-solar abundance m_Na/m_Ca > 900. The mass-loss rates and upper limits are tied to accretion in the white dwarfs, based on limiting cases for how the wind is captured, and compared with known cases of wind pollution from close M dwarf companions, which manifest in solar proportions between all elements detected. For wind captured in a Bondi-Hoyle flow, mass-loss limits $\dot{M}\lesssim 5\times 10^{-17}$ ${\rm M}_\odot \, {\rm yr}^{-1}$ are established for three L dwarfs, while for M dwarfs polluting their hosts, winds in the range 10^-13-10^-16 ${\rm M}_\odot \, {\rm yr}^{-1}$ are found. The latter compares well with the $\dot{M}\sim 10^{-13} {\!-\!} 10^{-15}$ ${\rm M}_\odot \, {\rm yr}^{-1}$ estimates obtained for nearby, isolated M dwarfs using Ly$\alpha$ to probe their astropsheres. These results demonstrate that white dwarfs are highly sensitive stellar and substellar wind detectors, where further work on the actual captured wind flow is needed.

October 2023: Walters, N; Farihi, J; Dufour, P; Pineda, J; Izzard, R (Monthly Notices of the Royal Astronomical Society)

Characterizing a World Within the Hot-Neptune Desert: Transit Observations of LTT 9779 b with the Hubble Space Telescope/WFC3

We present an atmospheric analysis of LTT 9779 b, a rare planet situated in the hot-Neptune desert, that has been observed with Hubble Space Telescope (HST)/WFC3 with G102 and G141. The combined transmission spectrum, which covers 0.8-1.6 μm, shows a gradual increase in transit depth with wavelength. Our preferred atmospheric model shows evidence for H₂O, CO₂, and FeH with a significance of 3.1σ, 2.4σ, and 2.1σ, respectively. In an attempt to constrain the rate of atmospheric escape for this planet, we search for the 1.083 μm helium line in the G102 data but find no evidence of excess absorption that would indicate an escaping atmosphere using this tracer. We refine the orbital ephemerides of LTT 9779 b using our HST data and observations from TESS, searching for evidence of orbital decay or apsidal precession, which are not found. The phase-curve observation of LTT 9779 b with JWST NIRISS should provide deeper insights into the atmosphere of this planet and the expected atmospheric escape might be detected with further observations concentrated on other tracers such as Lyα.

October 2023: Edwards, B; Changeat, Q; Tsiaras, A; Allan, A; Behr, P; et al. (The Astronomical Journal)

Planet gap-opening feedback on disk thermal structure and composition

(Exo-)planets inherit their budget of chemical elements from a protoplanetary disk. The disk temperature determines the phase of each chemical species, which sets the composition of solids and gas available for planet formation. We investigate how gap structures, which are widely seen by recent disk observations, alter the thermal and chemical structure of a disk. Planet-disk interaction is a leading hypothesis of gap formation and so such changes could present a feedback that planets have on planet-forming material. Both the planet gap-opening process and the disk thermal structure are well studied individually, but how the gap-opening process affects disk thermal structure evolution remains an open question. We develop a new modelling method by iterating hydrodynamical and radiative transfer simulations to explore the gap-opening feedback on disk thermal structure. We carry out parameter studies by considering different planet locations r_p and planet masses M_p. We find that for the same r_p and M_p, our iteration method predicts a wider and deeper gap than the non-iteration method. We also find that the inner disk and gap temperature from the iteration method can vary strongly from the non-iteration or disk without planets, which can further influence dust-trap conditions, iceline locations, and distribution of various ices, such as H₂O, CO₂, and CO on large dust grains ('pebbles'). Through that, a gap-opening planet can complicate the canonical picture of the non-planet disk C/O ratio and influence the composition of the next generation of planetesimals and planets.

October 2023: Chen, K; Kama, M; Pinilla, P; Keyte, L (Monthly Notices of the Royal Astronomical Society)

Constraining the atmospheric elements in hot Jupiters with Ariel

One of the main objectives of the European Space Agency's Ariel telescope (launch 2029) is to understand the formation and evolution processes of a large sample of planets in our Galaxy. Important indicators of such processes in giant planets are the elemental compositions of their atmospheres. Here we investigate the capability of Ariel to constrain four key atmospheric markers: metallicity, C/O, S/O, and N/O, for three well-known, representative hot-Jupiter atmospheres observed with transit spectroscopy, i.e. HD 209458b, HD 189733b, and WASP-121b. We have performed retrieval simulations for these targets to verify how the planetary formation markers listed above would be recovered by Ariel when observed as part of the Ariel Tier 3 survey. We have considered eight simplified different atmospheric scenarios with a cloud-free isothermal atmosphere. Additionally, extra cases were tested to illustrate the effect of C/O and metallicity in recovering the N/O. From our retrieval results, we conclude that Ariel is able to recover the majority of planetary formation markers. The contributions from CO and CO₂ are dominant for the C/O in the solar scenario. In a C-rich case, C₂H₂, HCN, and CH₄ may provide additional spectral signatures that can be captured by Ariel. In our simulations, H₂S is the main tracer for the S/O in hot-Jupiter atmospheres. In the super-solar metallicity cases and the cases with C/O > 1, the increased abundance of HCN is easily detectable and the main contributor to N/O, while other N-bearing species contribute little to the N/O in the investigated atmospheres.

August 2023: Wang, F; Changeat, Q; Tinetti, G; Turrini, D; Wright, S (Monthly Notices of the Royal Astronomical Society)

The period-luminosity relation for Mira variables in the Milky Way using Gaia DR3: a further distance anchor for H₀

Gaia DR3 parallaxes are used to calibrate preliminary period-luminosity relations of O-rich Mira variables in the 2MASS J, H, and K_s bands using a probabilistic model accounting for variations in the parallax zero-point and underestimation of the parallax uncertainties. The derived relations are compared to those measured for the Large and Small Magellanic Clouds, the Sagittarius dwarf spheroidal galaxy, globular cluster members, and the subset of Milky Way Mira variables with VLBI parallaxes. The Milky Way linear JHK_s relations are slightly steeper and thus fainter at short period than the corresponding LMC relations, suggesting population effects in the near-infrared are perhaps larger than previous observational works have claimed. Models of the Gaia astrometry for the Mira variables suggest that, despite the intrinsic photocentre wobble and use of mean photometry in the astrometric solution of the current data reduction, the recovered parallaxes should be on average unbiased but with underestimated uncertainties for the nearest stars. The recommended Gaia EDR3 parallax zero-point corrections evaluated at $\nu _\mathrm{eff}=1.25\, \mu \mathrm{m}^{-1}$ require minimal ($\lesssim 5\, \mu \mathrm{as}$) corrections for redder five-parameter sources, but overcorrect the parallaxes for redder six-parameter sources, and the parallax uncertainties are underestimated at most by a factor ~1.6 at $G\approx 12.5\, \mathrm{mag}$. The derived period-luminosity relations are used as anchors for the Mira variables in the Type Ia host galaxy NGC 1559 to find $H_0=(73.7\pm 4.4)\, \mathrm{km\, s}^{-1}\, \mathrm{Mpc}^{-1}$.

August 2023: Sanders, J (Monthly Notices of the Royal Astronomical Society)

The Alcock-Paczyński effect from Lyman-α forest correlations: analysis validation with synthetic data

The three-dimensional distribution of the Ly α forest has been extensively used to constrain cosmology through measurements of the baryon acoustic oscillations (BAO) scale. However, more cosmological information could be extracted from the full shapes of the Ly α forest correlations through the Alcock-Paczyński (AP) effect. In this work, we prepare for a cosmological analysis of the full shape of the Ly α forest correlations by studying synthetic data of the extended Baryon Oscillation Spectroscopic Survey (eBOSS). We use a set of 100 eBOSS synthetic data sets in order to validate such an analysis. These mocks undergo the same analysis process as the real data. We perform a full-shape analysis on the mean of the correlation functions measured from the 100 eBOSS realizations, and find that our model of the Ly α correlations performs well on current data sets. We show that we are able to obtain an unbiased full-shape measurement of D_M/D_H(z_eff), where D_M is the transverse comoving distance, D_H is the Hubble distance, and z_eff is the effective redshift of the measurement. We test the fit over a range of scales, and decide to use a minimum separation of r_min = 25 h^-1Mpc. We also study and discuss the impact of the main contaminants affecting Ly α forest correlations, and give recommendations on how to perform such analysis with real data. While the final eBOSS Ly α BAO analysis measured D_M/D_H(z_eff = 2.33) with 4 per cent statistical precision, a full-shape fit of the same correlations could provide an $\sim 2~{{\ \rm per\ cent}}$ measurement.

August 2023: Cuceu, A; Font-Ribera, A; Martini, P; Joachimi, B; Nadathur, S; et al. (Monthly Notices of the Royal Astronomical Society)

A Spectroscopic Thermometer: Individual Vibrational Band Spectroscopy with the Example of OH in the Atmosphere of WASP-33b

Individual vibrational band spectroscopy presents an opportunity to examine exoplanet atmospheres in detail, by distinguishing where the vibrational state populations of molecules differ from the current assumption of a Boltzmann distribution. Here, retrieving vibrational bands of OH in exoplanet atmospheres is explored using the hot Jupiter WASP-33b as an example. We simulate low-resolution spectroscopic data for observations with the JWST's NIRSpec instrument and use high-resolution observational data obtained from the Subaru InfraRed Doppler instrument (IRD). Vibrational band-specific OH cross-section sets are constructed and used in retrievals on the (simulated) low- and (real) high-resolution data. Low-resolution observations are simulated for two WASP-33b emission scenarios: under the assumption of local thermal equilibrium (LTE) and with a toy non-LTE model for vibrational excitation of selected bands. We show that mixing ratios for individual bands can be retrieved with sufficient precision to allow the vibrational population distributions of the forward models to be reconstructed. A fit for the Boltzmann distribution in the LTE case shows that the vibrational temperature is recoverable in this manner. For high-resolution, cross-correlation applications, we apply the individual vibrational band analysis to an IRD spectrum of WASP-33b, applying an "unpeeling" technique. Individual detection significances for the two strongest bands are shown to be in line with Boltzmann-distributed vibrational state populations, consistent with the effective temperature of the WASP-33b atmosphere reported previously. We show the viability of this approach for analyzing the individual vibrational state populations behind observed and simulated spectra, including reconstructing state population distributions.

August 2023: Wright, S; Nugroho, S; Brogi, M; Gibson, N; de Mooij, E; et al. (The Astronomical Journal)

The north-south asymmetry of the ALFALFA H I velocity width function

The number density of extragalactic 21-cm radio sources as a function of their spectral line widths - the H I width function (H I WF) - is a sensitive tracer of the dark matter halo mass function (HMF). The Lambda cold dark matter model predicts that the HMF should be identical everywhere provided it is sampled in sufficiently large volumes, implying that the same should be true of the H I WF. The Arecibo Legacy Fast ALFA (ALFALFA) 21-cm survey measured the H I WF in northern and southern Galactic fields and found a systematically higher number density in the north. At face value, this is in tension with theoretical predictions. We use the Sibelius-DARK N-body simulation and the semi-analytical galaxy formation model GALFORM to create a mock ALFALFA survey. We find that the offset in number density has two origins: the sensitivity of the survey is different in the two fields, which has not been correctly accounted for in previous measurements; and the 1/V_eff algorithm used for completeness corrections does not fully account for biases arising from spatial clustering in the galaxy distribution. The latter is primarily driven by a foreground overdensity in the northern field within $30\, \mathrm{Mpc}$ , but more distant structure also plays a role. We provide updated measurements of the ALFALFA H I WF (and H I mass function) correcting for the variations in survey sensitivity. Only when systematic effects such as these are understood and corrected for can cosmological models be tested against the H I WF.

July 2023: Brooks, R; Oman, K; Frenk, C (Monthly Notices of the Royal Astronomical Society)

The JCMT nearby galaxies legacy survey: SCUBA-2 observations of nearby galaxies

We present 850 $\mu$m observations of a sample of 8 nearby spiral galaxies, made using the SCUBA-2 camera on the James Clerk Maxwell Telescope (JCMT) as part of the JCMT Nearby Galaxies Legacy Survey (NGLS). We corrected our data for the presence of the ¹²CO J = 3 → 2 line in the SCUBA-2 850 $\mu$m bandwidth using NGLS HARP data, finding a typical ¹²CO contribution of ~20 per cent. We measured dust column densities, temperatures, and opacity indices by fitting spectral energy distributions constructed from SCUBA-2 and archival Herschel observations, and used archival GALEX and Spitzer data to make maps of surface density of star formation ($\Sigma _{\small {\rm SFR}}$). Typically, comparing SCUBA-2-derived H₂ surface densities ($\Sigma _{\rm H_2}$) to $\Sigma _{\small {\rm SFR}}$ gives shallow star formation law indices within galaxies, with SCUBA-2-derived values typically being sublinear and Herschel-derived values typically being broadly linear. This difference is likely due to the effects of atmospheric filtering on the SCUBA-2 data. Comparing the mean values of $\Sigma _{\rm H_2}$ and $\Sigma _{\small {\rm SFR}}$ of the galaxies in our sample returns a steeper star formation law index, broadly consistent with both the Kennicutt-Schmidt value of 1.4 and linearity. Our results show that a SCUBA-2 detection is a good predictor of star formation. We suggest that Herschel emission traces gas in regions which will form stars on time-scales ~5 - 100 Myr, comparable to the star formation time-scale traced by GALEX and Spitzer data, while SCUBA-2 preferentially traces the densest gas within these regions, which likely forms stars on shorter time-scales.

June 2023: Pattle, K; Gear, W; Wilson, C (Monthly Notices of the Royal Astronomical Society)

A low-metallicity massive contact binary undergoing slow Case A mass transfer: A detailed spectroscopic and orbital analysis of SSN 7 in NGC 346 in the SMC

Context. Most massive stars are believed to be born in close binary systems where they can exchange mass, which impacts the evolution of both binary components. Their evolution is of great interest in the search for the progenitors of gravitational waves. However, there are unknowns in the physics of mass transfer as observational examples are rare, especially at low metallicity. Nearby low-metallicity environments are particularly interesting hunting grounds for interacting systems as they act as the closest proxy for the early universe where we can resolve individual stars.
Aims: Using multi-epoch spectroscopic data, we complete a consistent spectral and orbital analysis of the early-type massive binary SSN 7 hosting a ON3 If^*+O5.5 V((f)) star. Using these detailed results, we constrain an evolutionary scenario that can help us to understand binary evolution in low metallicity.
Methods: We were able to derive reliable radial velocities of the two components from the multi-epoch data, which were used to constrain the orbital parameters. The spectroscopic data covers the UV, optical, and near-IR, allowing a consistent analysis with the stellar atmosphere code, PoWR. Given the stellar and orbital parameters, we interpreted the results using binary evolutionary models.
Results: The two stars in the system have comparable luminosities of log(L₁/L_⊙) = 5.75 and log(L₂/L_⊙) = 5.78 for the primary and secondary, respectively, but have different temperatures (T₁ = 43.6 kK and T₂ = 38.7 kK). The primary (32 M_⊙) is less massive than the secondary (55 M_⊙), suggesting mass exchange. The mass estimates are confirmed by the orbital analysis. The revisited orbital period is 3 d. Our evolutionary models also predict mass exchange. Currently, the system is a contact binary undergoing a slow Case A phase, making it the most massive Algol-like system yet discovered.
Conclusions: Following the initial mass function, massive stars are rare, and to find them in an Algol-like configuration is even more unlikely. To date, no comparable system to SSN 7 has been found, making it a unique object to study the efficiency of mass transfer in massive star binaries. This example increases our understanding of massive star binary evolution and the formation of gravitational wave progenitors.

Based on observations with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-2655. Also based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere.

June 2023: Rickard, M; Pauli, D (Astronomy and Astrophysics)

Measurement of stellar and substellar winds using white dwarf hosts

White dwarfs stars are known to be polluted by their active planetary systems, but little attention has been paid to the accretion of wind from low-mass companions. The capture of stellar or substellar wind by white dwarfs is one of few methods available to astronomers which can assess mass-loss rates from unevolved stars and brown dwarfs, and the only known method to extract their chemical compositions. In this work, four white dwarfs with closely-orbiting, L-type brown dwarf companions are studied to place limits on the accretion of a substellar wind, with one case of a detection, and at an extremely non-solar abundance m_Na/m_Ca > 900. The mass-loss rates and upper limits are tied to accretion in the white dwarfs, based on limiting cases for how the wind is captured, and compared with known cases of wind pollution from close M dwarf companions, which manifest in solar proportions between all elements detected. For wind captured in a Bondi-Hoyle flow, mass-loss limits $\dot{M}\lesssim 5\times 10^{-17}$ M_⊙ yr^-1are established for three L dwarfs, while for M dwarfs polluting their hosts, winds in the range 10^-13 - 10^-16 M_⊙ yr^-1are found. The latter compares well with the $\dot{M}\sim 10^{-13} - 10^{-15}$ M_⊙ yr^-1estimates obtained for nearby, isolated M dwarfs using Lyα to probe their astropsheres. These results demonstrate that white dwarfs are highly-sensitive stellar and substellar wind detectors, where further work on the actual captured wind flow is needed.

June 2023: Walters, N; Farihi, J; Dufour, P; Pineda, J; Izzard, R (Monthly Notices of the Royal Astronomical Society)

A robust estimator of mutual information for deep learning interpretability

We develop the use of mutual information (MI), a well-established metric in information theory, to interpret the inner workings of deep learning (DL) models. To accurately estimate MI from a finite number of samples, we present GMM-MI (pronounced 'Jimmie'), an algorithm based on Gaussian mixture models that can be applied to both discrete and continuous settings. GMM-MI is computationally efficient, robust to the choice of hyperparameters and provides the uncertainty on the MI estimate due to the finite sample size. We extensively validate GMM-MI on toy data for which the ground truth MI is known, comparing its performance against established MI estimators. We then demonstrate the use of our MI estimator in the context of representation learning, working with synthetic data and physical datasets describing highly non-linear processes. We train DL models to encode high-dimensional data within a meaningful compressed (latent) representation, and use GMM-MI to quantify both the level of disentanglement between the latent variables, and their association with relevant physical quantities, thus unlocking the interpretability of the latent representation. We make GMM-MI publicly available in this GitHub repository.

June 2023: Piras, D; Peiris, H; Pontzen, A; Lucie-Smith, L; Guo, N; et al. (Machine Learning: Science and Technology)

Azimuthal C/O variations in a planet-forming disk

The elemental carbon-to-oxygen ratio (C/O) in the atmosphere of a giant planet is a promising diagnostic of that planet's formation history in a protoplanetary disk. Alongside efforts in the exoplanet community to measure the C/O ratio in planetary atmospheres, observational and theoretical studies of disks are increasingly focused on understanding how the gas-phase C/O ratio varies both with radial location and between disks. This is mostly tied to the icelines of major volatile carriers such as CO and H₂O. Using ALMA observations of CS and SO, we have found evidence for an entirely unexpected type of C/O variation in the protoplanetary disk around HD 100546: an azimuthal variation from a typical, oxygen-dominated ratio (C/O ≈ 0.5) to a carbon-dominated ratio (C/O ≳ 1.0). We show that the spatial distribution and peculiar line kinematics of both CS and SO molecules can be well explained by azimuthal variations in the C/O ratio. We propose a shadowing mechanism that could lead to such a chemical dichotomy. Our results imply that tracing the formation history of giant exoplanets using their atmospheric C/O ratios will need to take into account time-dependent azimuthal C/O variations in a planet's accretion zone.

June 2023: Keyte, L; Kama, M; Booth, A; Bergin, E; Cleeves, L; et al. (Nature Astronomy)

Robust sampling for weak lensing and clustering analyses with the Dark Energy Survey

Recent cosmological analyses rely on the ability to accurately sample from high-dimensional posterior distributions. A variety of algorithms have been applied in the field, but justification of the particular sampler choice and settings is often lacking. Here, we investigate three such samplers to motivate and validate the algorithm and settings used for the Dark Energy Survey (DES) analyses of the first 3 yr (Y3) of data from combined measurements of weak lensing and galaxy clustering. We employ the full DES Year 1 likelihood alongside a much faster approximate likelihood, which enables us to assess the outcomes from each sampler choice and demonstrate the robustness of our full results. We find that the ellipsoidal nested sampling algorithm MULTINEST reports inconsistent estimates of the Bayesian evidence and somewhat narrower parameter credible intervals than the sliced nested sampling implemented in POLYCHORD. We compare the findings from MULTINEST and POLYCHORD with parameter inference from the Metropolis-Hastings algorithm, finding good agreement. We determine that POLYCHORD provides a good balance of speed and robustness for posterior and evidence estimation, and recommend different settings for testing purposes and final chains for analyses with DES Y3 data. Our methodology can readily be reproduced to obtain suitable sampler settings for future surveys.

May 2023: Lemos, P; Weaverdyck, N; Rollins, R; Muir, J; Ferte, A; et al. (Monthly Notices of the Royal Astronomical Society)

Hunting for C-rich long-period variable stars in the Milky Way's bar-bulge using unsupervised classification of Gaia BP/RP spectra

The separation of oxygen- and carbon-rich asymptotic giant branch sources is crucial for their accurate use as local and cosmological distance and age/metallicity indicators. We investigate the use of unsupervised learning algorithms for classifying the chemistry of long-period variables from Gaia DR3's BP/RP spectra. Even in the presence of significant interstellar dust, the spectra separate into two groups attributable to O-rich and C-rich sources. Given these classifications, we utilize a supervised approach to separate O-rich and C-rich sources without blue and red photometers (BP/RP) spectra but instead given broadband optical and infrared photometry finding a purity of our C-rich classifications of around 95 per cent. We test and validate the classifications against other advocated colour-colour separations based on photometry. Furthermore, we demonstrate the potential of BP/RP spectra for finding S-type stars or those possibly symbiotic sources with strong emission lines. Although our classification suggests the Galactic bar-bulge is host to very few C-rich long-period variable stars, we do find a small fraction of C-rich stars with periods $\gt 250\, \mathrm{day}$ that are spatially and kinematically consistent with bar-bulge membership. We argue the combination of the observed number, the spatial alignment, the kinematics, and the period distribution disfavour young metal-poor star formation scenarios either in situ or in an accreted host, and instead, these stars are highly likely to be the result of binary evolution and the evolved versions of blue straggler stars already observed in the bar-bulge.

May 2023: Sanders, J; Matsunaga, N (Monthly Notices of the Royal Astronomical Society)

A kinematic calibration of the O-rich Mira variable period-age relation from Gaia

Empirical and theoretical studies have demonstrated that the periods of Mira variable stars are related to their ages. This, together with their brightness in the infrared, makes them powerful probes of the formation and evolution of highly-extincted or distant parts of the Local Group. Here we utilize the Gaia DR3 catalogue of long-period variable candidates to calibrate the period-age relation of the Mira variables. Dynamical models are fitted to the O-rich Mira variable population across the extended solar neighbourhood and then the resulting solar neighbourhood period-kinematic relations are compared to external calibrations of the age-kinematic relations to derive a Mira variable period-age relation of $\tau \approx (6.9\pm 0.3)\, \mathrm{Gyr}(1+\tanh ((330\, \mathrm{d}-P)/(400\pm 90)\mathrm{d})$. Our results compare well with previous calibrations using smaller data sets as well as the period-age properties of Local Group cluster members. This calibration opens the possibility of accurately characterizing the star formation and the impact of different evolutionary processes throughout the Local Group.

May 2023: Zhang, H; Sanders, J (Monthly Notices of the Royal Astronomical Society)

Constraints on the Cosmic Expansion Rate at Redshift 2.3 from the Lyman-α Forest

We determine the product of the expansion rate and angular-diameter distance at redshift z =2.3 from the anisotropy of Lyman-α (Ly α ) forest correlations measured by the Sloan Digital Sky Survey (SDSS). Our result is the most precise from large-scale structure at z >1 . Using the flat Λ cold dark matter model we determine the matter density to be Ω_m=0.3 6_-0.04^+0.03 from Ly α alone. This is a factor of 2 tighter than baryon acoustic oscillation results from the same data due to our use of a wide range of scales (25 <r <180 h^-1 Mpc ). Using a nucleosynthesis prior, we measure the Hubble constant to be H₀=63.2 ±2.5 km /s /Mpc . In combination with other SDSS tracers, we find H₀=67.2 ±0.9 km /s /Mpc and measure the dark energy equation-of-state parameter to be w =-0.90 ±0.12 . Our Letter opens a new avenue for constraining cosmology at high redshift.

May 2023: Cuceu, A; Font-Ribera, A; Nadathur, S; Joachimi, B; Martini, P (Physical Review Letters)

Magnetic Fields in the Horsehead Nebula

We present the first polarized dust emission measurements of the Horsehead Nebula, obtained using the POL-2 polarimeter on the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) camera on the James Clerk Maxwell Telescope. The Horsehead Nebula contains two submillimeter sources: a photodissociation region (PDR; SMM1) and a starless core (SMM2). We see well-ordered magnetic fields in both sources. We estimated plane-of-sky magnetic field strengths of 56 ± 9 and 129 ± 21 μG in SMM1 and SMM2, respectively, and obtained mass-to-flux ratios and Alfvén Mach numbers of less than 0.6, suggesting that the magnetic field can resist gravitational collapse and that magnetic pressure exceeds internal turbulent pressure in these sources. In SMM2, the kinetic and gravitational energies are comparable to one another, but less than the magnetic energy. We suggest a schematic view of the overall magnetic field structure in the Horsehead Nebula. Magnetic field lines in SMM1 appear to have been compressed and reordered during the formation of the PDR, while the likely more-embedded SMM2 may have inherited its field from that of the pre-shock molecular cloud. The magnetic fields appear to currently play an important role in supporting both sources.

May 2023: Hwang, J; Pattle, K; Parsons, H; Go, M; Kim, J (The Astronomical Journal)

ExoMol line lists - XLVII. Rovibronic spectrum of aluminium monochloride (AlCl)

A line list for two isotopologues of aluminium monochloride, Al³⁵Cl and Al³⁷Cl, is presented covering the wavelength range <0.2 µm, J up to 400, and applicable for temperatures up to 5000 K. The line lists are built using an empirical spectroscopic model consisting of potential energy curves, spin-orbit coupling curves, electronic angular momentum curves, and Born-Oppenheimer breakdown correction curves combined with ab initio dipole moments and cover the four lowest electronic states, ${X}\, ^1\Sigma ^+$, ${A}\, ^1\Pi$, ${a}\, ^3\Pi$, and ${b}\, ^3\Sigma ^+$. Considerable problems with the assignments of some laboratory rovibronic spectra are identified. Treatment of the states lying in the continuum is discussed. The YNAT line list is available from the ExoMol data base at www.exomol.com.

April 2023: Yurchenko, S; Nogue, E; Azzam, A; Tennyson, J (Monthly Notices of the Royal Astronomical Society)

ExoMol line lists - XLVIII. High-temperature line list of thioformaldehyde (H₂CS)

A comprehensive rotation-vibration (ro-vibrational) line list of thioformaldehyde (¹H₂¹²C³²S) that is applicable for elevated temperatures (${2000}{\, \mathrm{K}}$) is presented. The new MOTY line list covers the 0-8000 cm^-1 range (wavelengths $\lambda \gt {1.3}{\, \mu \mathrm{m}})$ and contains around 43.5 billion transitions between 52.3 million states with rotational excitation up to J = 120. Line list calculations utilize a newly determined empirically refined potential energy surface (PES) - the most accurate H₂CS PES to date - a previously published high-level ab initio dipole moment surface, and the use of an exact kinetic energy operator for solving the ro-vibrational Schrödinger equation. Post-processing of the MOTY line list is performed by replacing calculated energy levels with empirically derived values, vastly improving the accuracy of predicted line positions in certain spectral windows and making the line list suitable for high-resolution applications. The MOTY line list is available from the ExoMol data base at www.exomol.com and the CDS astronomical data base.

April 2023: Mellor, T; Owens, A; Tennyson, J; Yurchenko, S (Monthly Notices of the Royal Astronomical Society)

Understanding and predicting cadence effects in the characterization of exoplanet transits

We investigate the effect of observing cadence on the precision of radius ratio values obtained from transit light curves by performing uniform Markov chain Monte Carlo fits of 46 exoplanets observed by the Transiting Exoplanet Survey Satellite (TESS) in multiple cadences. We find median improvements of almost 50 per cent when comparing fits to 20 and 120 s cadence light curves to 1800 s cadence light curves, and of 37 per cent when comparing 600 s cadence to 1800 s cadence. Such improvements in radius precision are important, for example, to precisely constrain the properties of the radius valley or to characterize exoplanet atmospheres. We also implement a numerical information analysis to predict the precision of parameter estimates for different observing cadences. We tested this analysis on our sample and found that it reliably predicts the effect of shortening observing cadence with errors in the predicted percentage precision of $\lesssim0.5~{{\ \rm per\ cent}}$ for most cases. We apply this method to 157 TESS objects of interest that have only been observed with 1800 s cadence to predict the precision improvement that could be obtained by reobservations with shorter cadences and provide the full table of expected improvements. We report the 10 planet candidates that would benefit the most from reobservations at short cadence. Our implementation of the information analysis for the prediction of the precision of exoplanet parameters, Prediction of Exoplanet Precisions using Information in Transit Analysis, is made publicly available.

April 2023: Hernandez Camero, J; Ho, C; Van Eylen, V (Monthly Notices of the Royal Astronomical Society)

Dust survival rates in clumps passing through the Cas A reverse shock - II. The impact of magnetic fields

Dust grains form in the clumpy ejecta of core-collapse supernovae where they are subject to the reverse shock, which is able to disrupt the clumps and destroy the grains. Important dust destruction processes include thermal and kinetic sputtering as well as fragmentation and grain vaporization. In the present study, we focus on the effect of magnetic fields on the destruction processes. We have performed magnetohydrodynamical simulations using ASTROBEAR to model a shock wave interacting with an ejecta clump. The dust transport and destruction fractions are computed using our post-processing code PAPERBOATS, in which the acceleration of grains due to the magnetic field and a procedure that allows partial grain vaporization have been newly implemented. For the oxygen-rich supernova remnant Cassiopeia A, we found a significantly lower dust survival rate when magnetic fields are aligned perpendicular to the shock direction compared to the non-magnetic case. For a parallel field alignment, the destruction is also enhanced but at a lower level. The survival fractions depend sensitively on the gas density contrast between the clump and the ambient medium and on the grain sizes. For a low-density contrast of 100, e.g. 5 nm silicate grains are completely destroyed while the survival fraction of $1\,\mu{\rm m}$ grains is 86 per cent. For a high-density contrast of 1000, 95 per cent of the 5 nm grains survive while the survival fraction of $1\,\mu{\rm m}$ grains is 26 per cent. Alternative clump sizes or dust materials (carbon) have non-negligible effects on the survival rate but have a lower impact compared to density contrast, magnetic field strength, and grain size.

April 2023: Kirchschlager, F; Schmidt, F; Barlow, M; De Looze, I; Sartorio, N (Monthly Notices of the Royal Astronomical Society)

The north-south asymmetry of the ALFALFA H I velocity width function

The number density of extragalactic 21-cm radio sources as a function of their spectral line-widths - the H I width function (H I WF) - is a sensitive tracer of the dark matter halo mass function (HMF). The Λ cold dark matter model predicts that the HMF should be identical everywhere provided it is sampled in sufficiently large volumes, implying that the same should be true of the H I WF. The ALFALFA 21-cm survey measured the H I WF in northern and southern Galactic fields and found a systematically higher number density in the north. At face value, this is in tension with theoretical predictions. We use the Sibelius-DARK N-body simulation and the semi-analytical galaxy formation model GALFORM to create a mock ALFALFA survey. We find that the offset in number density has two origins: the sensitivity of the survey is different in the two fields, which has not been correctly accounted for in previous measurements; and the 1/V_eff algorithm used for completeness corrections does not fully account for biases arising from spatial clustering in the galaxy distribution. The latter is primarily driven by a foreground overdensity in the northern field within 30 Mpc, but more distant structure also plays a role. We provide updated measurements of the ALFALFA H I WF (and H I MF) correcting for the variations in survey sensitivity. Only when systematic effects such as these are understood and corrected for can cosmological models be tested against the H I WF.

April 2023: Brooks, R; Oman, K; Frenk, C (Monthly Notices of the Royal Astronomical Society)

Azimuthal C/O variations in a planet-forming disk

April 2023: Keyte, L; Kama, M; Booth, A; Bergin, E; Cleeves, L; et al. (Nature Astronomy)

Impact of Rubin Observatory Cadence Choices on Supernovae Photometric Classification

The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will discover an unprecedented number of supernovae (SNe), making spectroscopic classification for all the events infeasible. LSST will thus rely on photometric classification, whose accuracy depends on the not-yet-finalized LSST observing strategy. In this work, we analyze the impact of cadence choices on classification performance using simulated multiband light curves. First, we simulate SNe with an LSST baseline cadence, a nonrolling cadence, and a presto-color cadence, which observes each sky location three times per night instead of twice. Each simulated data set includes a spectroscopically confirmed training set, which we augment to be representative of the test set as part of the classification pipeline. Then we use the photometric transient classification library snmachine to build classifiers. We find that the active region of the rolling cadence used in the baseline observing strategy yields a 25% improvement in classification performance relative to the background region. This improvement in performance in the actively rolling region is also associated with an increase of up to a factor of 2.7 in the number of cosmologically useful Type Ia SNe relative to the background region. However, adding a third visit per night as implemented in presto-color degrades classification performance due to more irregularly sampled light curves. Overall, our results establish desiderata on the observing cadence related to classification of full SNe light curves, which in turn impacts photometric SNe cosmology with LSST.

April 2023: Alves, C; Peiris, H; Lochner, M; McEwen, J; Kessler, R; et al. (The Astrophysical Journal Supplement Series)

The JCMT Nearby Galaxies Legacy Survey: SCUBA-2 observations of nearby galaxies

We present 850μm observations of a sample of 8 nearby spiral galaxies, made using the SCUBA-2 camera on the James Clerk Maxwell Telescope (JCMT) as part of the JCMT Nearby Galaxies Legacy Survey (NGLS). We corrected our data for the presence of the ¹²CO J = 3 → 2 line in the SCUBA-2 850μm bandwidth using NGLS HARP data, finding a typical ¹²CO contribution of ~20%. We measured dust column densities, temperatures and opacity indices by fitting spectral energy distributions constructed from SCUBA-2 and archival Herschel observations, and used archival GALEX and Spitzer data to make maps of surface density of star formation ($\Sigma _{\small {SFR}}$). Typically, comparing SCUBA-2-derived H₂ surface densities ($\Sigma _{\rm H_2}$) to $\Sigma _{\small {SFR}}$ gives shallow star formation law indices within galaxies, with SCUBA-2-derived values typically being sublinear and Herschel-derived values typically being broadly linear. This difference is likely due to the effects of atmospheric filtering on the SCUBA-2 data. Comparing the mean values of $\Sigma _{\rm H_2}$ and $\Sigma _{\small {SFR}}$ of the galaxies in our sample returns a steeper star formation law index, broadly consistent with both the Kennicutt-Schmidt value of 1.4 and linearity. Our results show that a SCUBA-2 detection is a good predictor of star formation. We suggest that Herschel emission traces gas in regions which will form stars on timescales ~5 - 100 Myr, comparable to the star formation timescale traced by GALEX and Spitzer data, while SCUBA-2 preferentially traces the densest gas within these regions, which likely forms stars on shorter timescales.

March 2023: Pattle, K; Gear, W; Wilson, C (Monthly Notices of the Royal Astronomical Society)

The impact of weak lensing on Type Ia supernovae luminosity distances

When Type Ia supernovae are used to infer cosmological parameters, their luminosities are compared to those from a homogeneous cosmology. In this note, we propose a test to examine to what degree SN Ia have been observed on lines of sight where the average matter density is not representative of the homogeneous background. We apply our test to the Pantheon SN Ia compilation, and find two redshift bins which indicate a moderate bias to over-density at ~2σ. We modify the Tripp estimator to explicitly de-lens SN Ia magnitudes, and show that this reduces scatter of Hubble diagram residuals. Using our revised Tripp estimator, the effect on cosmological parameters from Pantheon in ΛCDM is however small with a change in mean value from Ω_m = 0.317 ± 0.027 (baseline) to Ω_m = 0.312 ± 0.025 (de-lensed). For the Flat wCDM case, it is Ω_m = 0.332 ± 0.049 and w = -1.16 ± 0.16 (baseline) versus Ω_m = 0.316 ± 0.048 and w = -1.12 ± 0.15 (de-lensed). We note that the effect of lensing on cosmological parameters may be larger for future high-z surveys.

March 2023: Shah, P; Lemos, P; Lahav, O (Monthly Notices of the Royal Astronomical Society)

Investigating the impact of reactions of C and CH with molecular hydrogen on a glycine gas-grain network

The impact of including the reactions of C and CH with molecular hydrogen in a gas-grain network is assessed via a sensitivity analysis. To this end, we vary three parameters, namely, the efficiency for the reaction ${\rm C} + {\rm H}_2 \longrightarrow {\rm CH}_{2}$, and the cosmic ray ionization rate, with the third parameter being the final density of the collapsing dark cloud. A grid of 12 models is run to investigate the effect of all parameters on the final molecular abundances of the chemical network. We find that including reactions with molecular hydrogen alters the hydrogen economy of the network; since some species are hydrogenated by molecular hydrogen, atomic hydrogen is freed up. The abundances of simple molecules produced from hydrogenation, such as CH₄, CH₃OH, and NH₃, increase, and at the same time, more complex species such as glycine and its precursors see a significant decrease in their final abundances. We find that the precursors of glycine are being preferentially hydrogenated, and therefore glycine itself is produced less efficiently.

March 2023: Heyl, J; Lamberts, T; Viti, S; Holdship, J (Monthly Notices of the Royal Astronomical Society)

ExoMol line lists - L: high-resolution line lists of H₃⁺, H₂D⁺, D₂H⁺, and D₃⁺

New MiZo line lists are presented for the D₂H⁺ and D$_3^+$ isotopologues of H$_3^+$. These line lists plus the existing H$_3^+$ MiZATeP and the ST H₂D⁺ line lists are updated using empirical energy levels generated using the MARVEL procedure for H$_3^+$, H₂D⁺, and D₂H⁺, and effective Hamiltonian energies for D$_3^+$ for which there is significantly less laboratory data available. These updates allow accurate frequencies for far infrared lines for these species to be predicted. Assignments of the energy levels of H$_3^+$ and D$_3^+$ are extended using a combination of high accuracy variational calculations and analysis of transition intensities. All line lists are made av ailable via www.exomol.com.

March 2023: Bowesman, C; Mizus, I; Zobov, N; Polyansky, O; Sarka, J; et al. (Monthly Notices of the Royal Astronomical Society)

Robust simulation-based inference in cosmology with Bayesian neural networks

Simulation-based inference (SBI) is rapidly establishing itself as a standard machine learning technique for analyzing data in cosmological surveys. Despite continual improvements to the quality of density estimation by learned models, applications of such techniques to real data are entirely reliant on the generalization power of neural networks far outside the training distribution, which is mostly unconstrained. Due to the imperfections in scientist-created simulations, and the large computational expense of generating all possible parameter combinations, SBI methods in cosmology are vulnerable to such generalization issues. Here, we discuss the effects of both issues, and show how using a Bayesian neural network framework for training SBI can mitigate biases, and result in more reliable inference outside the training set. We introduce cosmoSWAG, the first application of stochastic weight averaging to cosmology, and apply it to SBI trained for inference on the cosmic microwave background.

March 2023: Lemos, P; Cranmer, M; Abidi, M; Hahn, C; Eickenberg, M; et al. (Machine Learning: Science and Technology)

Fast and realistic large-scale structure from machine-learning-augmented random field simulations

Producing thousands of simulations of the dark matter distribution in the Universe with increasing precision is a challenging but critical task to facilitate the exploitation of current and forthcoming cosmological surveys. Many inexpensive substitutes to full N-body simulations have been proposed, even though they often fail to reproduce the statistics of the smaller non-linear scales. Among these alternatives, a common approximation is represented by the lognormal distribution, which comes with its own limitations as well, while being extremely fast to compute even for high-resolution density fields. In this work, we train a generative deep learning model, mainly made of convolutional layers, to transform projected lognormal dark matter density fields to more realistic dark matter maps, as obtained from full N-body simulations. We detail the procedure that we follow to generate highly correlated pairs of lognormal and simulated maps, which we use as our training data, exploiting the information of the Fourier phases. We demonstrate the performance of our model comparing various statistical tests with different field resolutions, redshifts, and cosmological parameters, proving its robustness and explaining its current limitations. When evaluated on 100 test maps, the augmented lognormal random fields reproduce the power spectrum up to wavenumbers of $1 \, h \, \rm {Mpc}^{-1}$, and the bispectrum within 10 per cent, and always within the error bars, of the fiducial target simulations. Finally, we describe how we plan to integrate our proposed model with existing tools to yield more accurate spherical random fields for weak lensing analysis.

March 2023: Piras, D; Joachimi, B; Villaescusa-Navarro, F (Monthly Notices of the Royal Astronomical Society)

Compressing the Cosmological Information in One-dimensional Correlations of the Lyα Forest

Observations of the Lyα forest from spectroscopic surveys such as the Baryon Oscillation Spectroscopic Survey or its extension, eBOSS, or the ongoing Dark Energy Spectroscopic Instrument (DESI) survey offer a unique window to study the growth of structure on megaparsec scales. Interpretation of these measurements is a complicated task, requiring hydrodynamical simulations to model and marginalize over the thermal and ionization state of the intergalactic medium. This complexity has limited the use of Lyα clustering measurements in joint cosmological analyses. In this work we show that the cosmological information content of the one-dimensional power spectrum (P _1D) of the Lyα forest can be compressed into a simple two-parameter likelihood without any significant loss of constraining power. We simulate P _1D measurements from DESI using hydrodynamical simulations and show that the compressed likelihood is model independent and lossless, recovering unbiased results even in the presence of massive neutrinos or running of the primordial power spectrum.

February 2023: Pedersen, C; Font-Ribera, A; Gnedin, N (The Astrophysical Journal)

Radiative transfer as a Bayesian linear regression problem

Electromagnetic radiation plays a crucial role in various physical and chemical processes. Hence, almost all astrophysical simulations require some form of radiative transfer model. Despite many innovations in radiative transfer algorithms and their implementation, realistic radiative transfer models remain very computationally expensive, such that one often has to resort to approximate descriptions. The complexity of these models makes it difficult to assess the validity of any approximation and to quantify uncertainties on the model results. This impedes scientific rigour, in particular, when comparing models to observations, or when using their results as input for other models. We present a probabilistic numerical approach to address these issues by treating radiative transfer as a Bayesian linear regression problem. This allows us to model uncertainties on the input and output of the model with the variances of the associated probability distributions. Furthermore, this approach naturally allows us to create reduced-order radiative transfer models with a quantifiable accuracy. These are approximate solutions to exact radiative transfer models, in contrast to the exact solutions to approximate models that are often used. As a first demonstration, we derive a probabilistic version of the method of characteristics, a commonly-used technique to solve radiative transfer problems.

February 2023: De Ceuster, F; Ceulemans, T; Cockayne, J; Decin, L; Yates, J (Monthly Notices of the Royal Astronomical Society)

Two substellar survivor candidates: one found and one missing

This study presents observations of two possible substellar survivors of post-main sequence engulfment, currently orbiting white dwarf stars. Infrared and optical spectroscopy of GD 1400 reveals a 9.98 h orbital period, where the benchmark brown dwarf has M₂ = 68 ± 8 M_Jup, T_eff ≈ 2100 K, and a cooling age under 1 Gyr. A substellar mass in the lower range of allowed values is favoured by the gravitational redshift of the primary. Synthetic brown dwarf spectra are able to reproduce the observed CO bands, but lines below the bandhead are notably overpredicted. The known infrared excess towards PG 0010+281 is consistent with a substellar companion, yet no radial velocity or photometric variability is found despite extensive searches. Three independent stellar mass determinations all suggest enhanced mass-loss associated with binary evolution, where the youngest total age for an isolated star is 7.5 ± 2.5 Gyr. A possible solution to this conundrum is the cannibalization of one or more giant planets, which enhanced mass-loss post-main sequence, but were ultimately destroyed. PG 0010 + 281 is likely orbited by a debris disc that is comfortably exterior to the Roche limit, adding to the growing number of non-canonical discs orbiting white dwarfs. At present, only L-type (brown) dwarfs are known to survive direct engulfment during the post-main sequence, whereas T- and Y-type substellar companions persist at wide separations. These demographics indicate that roughly 50 M_Jup is required to robustly avoid post-main sequence annihilation, suggesting all closely orbiting giant planets are consumed, which may contribute to mass-loss and magnetic-field generation in white dwarfs and their immediate progenitors.

February 2023: Walters, N; Farihi, J; Marsh, T; Breedt, E; Cauley, P; et al. (Monthly Notices of the Royal Astronomical Society)

Optimizing the shape of photometric redshift distributions with clustering cross-correlations

We present an optimization method for the assignment of photometric galaxies to a chosen set of redshift bins. This is achieved by combining simulated annealing, an optimization algorithm inspired by solid-state physics, with an unsupervised machine learning method, a self-organizing map (SOM) of the observed colours of galaxies. Starting with a sample of galaxies that is divided into redshift bins based on a photometric redshift point estimate, the simulated annealing algorithm repeatedly reassigns SOM-selected subsamples of galaxies, which are close in colour, to alternative redshift bins. We optimize the clustering cross-correlation signal between photometric galaxies and a reference sample of galaxies with well-calibrated redshifts. Depending on the effect on the clustering signal, the reassignment is either accepted or rejected. By dynamically increasing the resolution of the SOM, the algorithm eventually converges to a solution that minimizes the number of mismatched galaxies in each tomographic redshift bin and thus improves the compactness of their corresponding redshift distribution. This method is demonstrated on the synthetic Legacy Survey of Space and Time cosmoDC2 catalogue. We find a significant decrease in the fraction of catastrophic outliers in the redshift distribution in all tomographic bins, most notably in the highest redshift bin with a decrease in the outlier fraction from 57 per cent to 16 per cent.

February 2023: Stolzner, B; Joachimi, B; Korn, A; LSST Dark Energy Science Collaboration (Monthly Notices of the Royal Astronomical Society)

Constrained simulations of the local Universe with modified gravity

We present a methodology for constructing modified gravity (MG) constrained simulations of the local Universe using positions and peculiar velocities from the CosmicFlows data set. Our analysis focuses on the following MG models: the normal branch of the Dvali-Gabadadze-Porrati (nDGP) model and the Hu-Sawicki f (R ) model. We develop a model-independent methodology for constructing constrained simulations with any given power spectra and numerically calculated linear growth functions. Initial conditions (ICs) for a set of constrained simulations are constructed for the standard cosmological model Λ CDM and the MG models. Differences between the models' reconstructed Wiener filtered density and the resultant simulation density are presented showing the importance for the generation of MG constrained ICs to study the subtle effects of MG in the local Universe. These are the first MG constrained simulations ever produced. The current work paves the way to improved approximate methods for models with scale-dependent growth functions, such as f (R ), and for high-resolution hydrodynamical MG zoom-in simulations of the local Universe.

February 2023: Naidoo, K; Hellwing, W; Bilicki, M; Libeskind, N; Pfeifer, S; et al. (Physical Review D)

Euclid: Calibrating photometric redshifts with spectroscopic cross-correlations

Cosmological constraints from key probes of the Euclid imaging survey rely critically on the accurate determination of the true redshift distributions, n(z), of tomographic redshift bins. We determine whether the mean redshift, ⟨z⟩, of ten Euclid tomographic redshift bins can be calibrated to the Euclid target uncertainties of σ(⟨z⟩) < 0.002 (1 + z) via cross-correlation, with spectroscopic samples akin to those from the Baryon Oscillation Spectroscopic Survey (BOSS), Dark Energy Spectroscopic Instrument (DESI), and Euclid's NISP spectroscopic survey. We construct mock Euclid and spectroscopic galaxy samples from the Flagship simulation and measure small-scale clustering redshifts up to redshift z < 1.8 with an algorithm that performs well on current galaxy survey data. The clustering measurements are then fitted to two n(z) models: one is the true n(z) with a free mean; the other a Gaussian process modified to be restricted to non-negative values. We show that ⟨z⟩ is measured in each tomographic redshift bin to an accuracy of order 0.01 or better. By measuring the clustering redshifts on subsets of the full Flagship area, we construct scaling relations that allow us to extrapolate the method performance to larger sky areas than are currently available in the mock. For the full expected Euclid, BOSS, and DESI overlap region of approximately 6000 deg², the uncertainties attainable by clustering redshifts exceeds the Euclid requirement by at least a factor of three for both n(z) models considered, although systematic biases limit the accuracy. Clustering redshifts are an extremely effective method for redshift calibration for Euclid if the sources of systematic biases can be determined and removed, or calibrated out with sufficiently realistic simulations. We outline possible future work, in particular an extension to higher redshifts with quasar reference samples.

This paper is published on behalf of the Euclid Consortium.

February 2023: Naidoo, K; Johnston, H; Joachimi, B; van den Busch, J; Hildebrandt, H; et al. (Astronomy and Astrophysics)

Quantifying the dust in SN 2012aw and iPTF14hls with ORBYTS

Core-collapse supernovae (CCSNe) are capable of producing large quantities of dust, with strong evidence that ejecta dust masses can grow significantly over extended periods of time. Red-blue asymmetries in the broad emission lines of CCSNe can be modelled using the Monte Carlo radiative transfer code DAMOCLES, to determine ejecta dust masses. To facilitate easier use of DAMOCLES, we present a Tkinter graphical user interface (GUI) running DAMOCLES. The GUI was tested by high school students through the Original Research By Young Twinkle Students programme, who used it to measure the dust masses formed at two epochs in Type IIP CCSNe, SN 2012aw and iPTF14hls, demonstrating that a wide range of people can contribute to scientific advancement. Bayesian methods quantified uncertainties on our model parameters. From the red scattering wing in the day 1863 Hα profile of SN 2012aw, we constrained the dust composition to large (radius >0.1 μm) silicate grains, with a dust mass of $6.0^{+21.9}_{-3.6}\times 10^{-4}~\mathrm{ M}_\odot$. From the day 1158 Hα profile of SN 2012aw, we found a dust mass of $3.0^{+14}_{-2.5}\times 10^{-4}$ M_⊙. For iPTF14hls, we found a day 1170 dust mass of 8.1$^{+81}_{-7.6}\times 10^{-5}$ M_⊙ for a dust composition consisting of 50 per cent amorphous carbon and 50 per cent astronomical silicate. At 1000 d post-explosion, SN 2012aw and iPTF14hls have formed less dust than the peculiar Type II SN 1987A, suggesting that SN 1987A may have formed a larger dust mass than typical Type IIP's.

February 2023: Niculescu-Duvaz, M; Barlow, M; Dunn, W; Bevan, A; Ahmed, O; et al. (Monthly Notices of the Royal Astronomical Society)

ExoMol line lists - XLVIII. High-temperature line list of thioformaldehyde (H₂CS)

A comprehensive rotation-vibration (ro-vibrational) line list of thioformaldehyde (¹H₂¹²C³²S) that is applicable for elevated temperatures (2000K) is presented. The new MOTY line list covers the 0 to 8000 cm-1 range (wavelengths λ > 1.3μm and contains around 43.5billion transitions between 52.3million states with rotational excitation up to J = 120. Line list calculations utilise a newly determined empirically refined potential energy surface (PES) - the most accurate H₂CS PES to date - a previously published high-level ab initio dipole moment surface, and the use of an exact kinetic energy operator for solving the ro-vibrational Schrödinger equation. Post-processing of the MOTY line list is performed by replacing calculated energy levels with empirically-derived values, vastly improving the accuracy of predicted line positions in certain spectral windows and making the line list suitable for high-resolution applications. The MOTY line list is available from the ExoMol database at www.exomol.com and the CDS astronomical database.

January 2023: Mellor, T; Owens, A; Tennyson, J; Yurchenko, S (Monthly Notices of the Royal Astronomical Society)

KELT-9 and its ultra-hot Jupiter: Stellar parameters, composition, and planetary pollution

KELT-9b is an ultra-hot Jupiter observed to be undergoing extreme mass-loss. Its A0-type host star has a radiative envelope, which makes its surface layers prone to retaining recently accreted material. To search for potential signs of planetary material polluting the stellar surface, we carry out the most comprehensive chemical characterization of KELT-9 to-date. New element detections include Na and Y, which had previously been detected in the ultra-hot Jupiter but not studied in the star; these detections complete the set of ten elements measured in both star and planet. In comparing KELT-9 with similar open cluster stars we find no strong anomalies. This finding is consistent with calculations of photospheric pollution accounting for stellar mixing and using observationally estimated KELT-9b mass-loss rates. We also rule out recent, short-lived intensive mass transfer such as the stellar ingestion of an Earth-mass exomoon.

January 2023: Kama, M; Folsom, C; Jermyn, A; Teske, J (Monthly Notices of the Royal Astronomical Society)

The impact of weak lensing on Type Ia supernovae luminosity distances

When Type Ia supernovae are used to infer cosmological parameters, their luminosities are compared to those from a homogeneous cosmology. In this note we propose a test to examine to what degree SN Ia have been observed on lines of sight where the average matter density is not representative of the homogeneous background. We apply our test to the Pantheon SN Ia compilation, and find two redshift bins which indicate a moderate bias to over-density at ~2σ. We modify the Tripp estimator to explicitly de-lens SN Ia magnitudes, and show that this reduces scatter of Hubble diagram residuals. Using our revised Tripp estimator, the effect on cosmological parameters from Pantheon in ΛCDM is however small with a change in mean value from Ω_m = 0.317 ± 0.027 (baseline) to Ω_m = 0.312 ± 0.025 (de-lensed). For the Flat wCDM case it is Ω_m = 0.332 ± 0.049 and w = -1.16 ± 0.16 (baseline) versus Ω_m = 0.316 ± 0.048 and w = -1.12 ± 0.15 (de-lensed). We note that the effect of lensing on cosmological parameters may be larger for future high-z surveys.

January 2023: Shah, P; Lemos, P; Lahav, O (Monthly Notices of the Royal Astronomical Society)

Cold gas mass measurements for the era of large optical spectroscopic surveys

Gas plays an important role in many processes in galaxy formation and evolution, but quantifying the importance of gas has been hindered by the challenge to measure gas masses for large samples of galaxies. Data sets of direct atomic and molecular gas measurements are sufficient to establish simple scaling relations, but often not large enough to quantify three-parameter relations, or second-order dependences. As an alternative approach, we derive here indirect cold gas measurements from optical emission lines using photoionization models for galaxies in the Sloan Digital Sky Survey (SDSS) main galaxy sample and the PHANGS-MUSE survey. We calibrate the gas surface density measurements using xCOLD GASS and PHANGS-ALMA molecular gas measurements to ensure that our measurements are reliable. We demonstrate the importance of taking into account the scale dependence of the relation between optical depth (τ_V) and gas surface density (Σ_gas) and provide a general prescription to estimate Σ_gas from τ_V, metallicity, and the dust-to-metal ratio, at any arbitrary physical resolution. To demonstrate that the indirect cold gas masses are accurate enough to quantify the role of gas in galaxy evolution, we study the mass-metallicity relation of SDSS galaxies and show that as a third parameter gas mass is better than star formation rate at reducing the scatter of the relation, as predicted by models and simulations.

January 2023: Scholte, D; Saintonge, A (Monthly Notices of the Royal Astronomical Society)

Kinematics of molecular gas in star-forming galaxies with large-scale ionized outflows

We investigate the kinematics of the molecular gas in a sample of seven edge-on (i > 60°) galaxies identified as hosting large-scale outflows of ionized gas, using ALMA CO(1-0) observations at ~1 kpc resolution. We build on Hogarth et al., where we find that molecular gas is more centrally concentrated in galaxies which host winds than in control objects. We perform full three-dimensional kinematic modelling with multiple combinations of kinematic components, allowing us to infer whether these objects share any similarities in their molecular gas structure. We use modelling to pinpoint the kinematic centre of each galaxy, in order to interpret their minor- and major-axis position velocity diagrams (PVDs). From the PVDs, we find that the bulk of the molecular gas in our galaxies is dynamically cold, tracing the rotation curves predicted by our symmetric, rotation-dominated models, but with minor flux asymmetries. Most notably, we find evidence of radial gas motion in a subset of our objects, which demonstrate a characteristic 'twisting' in their minor-axis PVDs generally associated with gas flow along the plane of a galaxy. In our highest S/N object, we include bi-symmetric radial flow in our kinematic model, and find (via the Bayesian Information Criterion) that the presence of radial gas motion is strongly favoured. This may provide one mechanism by which molecular gas and star formation are centrally concentrated, enabling the launch of massive ionized gas winds. However, in the remainder of our sample, we do not observe evidence that gas is being driven radially, once again emphasizing the variety of physical processes that may be powering the outflows in these objects, as originally noted in H21.

January 2023: Hogarth, L; Saintonge, A; Davis, T (Monthly Notices of the Royal Astronomical Society)

Direct cosmological inference from three-dimensional correlations of the Lyman α forest

When performing cosmological inference, standard analyses of the Lyman α (Ly α) three-dimensional correlation functions only consider the information carried by the distinct peak produced by baryon acoustic oscillations (BAO). In this work, we address whether this compression is sufficient to capture all the relevant cosmological information carried by these functions. We do this by performing a direct fit to the full shape, including all physical scales without compression, of synthetic Ly α autocorrelation functions and cross-correlations with quasars at effective redshift z_eff = 2.3, assuming a DESI-like survey, and providing a comparison to the classic method applied to the same data set. Our approach leads to a $3.5{{\ \rm per\ cent}}$ constraint on the matter density Ω_M, which is about three to four times better than what BAO alone can probe. The growth term fσ₈(z_eff) is constrained to the $10{{\ \rm per\ cent}}$ level, and the spectral index n_s to $\sim 3-4{{\ \rm per\ cent}}$. We demonstrate that the extra information resulting from our 'direct fit' approach, except for the n_s constraint, can be traced back to the Alcock-Paczynski effect and redshift space distortion information.

January 2023: Gerardi, F; Cuceu, A; Font-Ribera, A; Joachimi, B; Lemos, P (Monthly Notices of the Royal Astronomical Society)

Modelling magnetic fields and plasma flows in the magnetosphere of Jupiter

The magnetic fields of the giant planets, Jupiter and Saturn, deviate significantly from a pure magnetic dipole and the cold plasma is mostly centrifugally confined near the equator. The additional contribution of the azimuthal currents leads to the stretching of the magnetic field and the formation of a characteristic, disc-type structure known as a magnetodisc. We present here an updated version of a numerical implementation of Caudal's iterative scheme, used to create models of the magnetosphere. In particular, we include newer equatorial density, temperature and hot plasma profiles obtained from Galileo data. Finally, we describe and use an algorithm to update the angular velocity profile after the end of the iterative process, using information from the magnetodisc. We also present comparisons between the azimuthal current and plasma flow predicted by our model and those derived from spacecraft observations.

January 2023: Millas, D; Achilleos, N; Guio, P; Arridge, C (Planetary and Space Science)

Dust survival rates in clumps passing through the Cas A reverse shock - II. The impact of magnetic fields

Dust grains form in the clumpy ejecta of core-collapse supernovae where they are subject to the reverse shock, which is able to disrupt the clumps and destroy the grains. Important dust destruction processes include thermal and kinetic sputtering as well as fragmentation and grain vaporization. In the present study, we focus on the effect of magnetic fields on the destruction processes. We have performed magneto-hydrodynamical simulations using ASTROBEAR to model a shock wave interacting with an ejecta clump. The dust transport and destruction fractions are computed using our post-processing code PAPERBOATS in which the acceleration of grains due to the magnetic field and a procedure that allows partial grain vaporization have been newly implemented. For the oxygen-rich supernova remnant Cassiopeia A we found a significantly lower dust survival rate when magnetic fields are aligned perpendicular to the shock direction compared to the non-magnetic case. For a parallel field alignment, the destruction is also enhanced but at a lower level. The survival fractions depend sensitively on the gas density contrast between the clump and the ambient medium and on the grain sizes. For a low-density contrast of 100, e.g., 5 nm silicate grains are completely destroyed while the survival fraction of 1 μm grains is 86 per cent. For a high-density contrast of 1000, 95 per cent of the 5 nm grains survive while the survival fraction of 1 μm grains is 26 per cent. Alternative clump sizes or dust materials (carbon) have non-negligible effects on the survival rate but have a lower impact compared to density contrast, magnetic field strength, and grain size.

January 2023: Kirchschlager, F; Schmidt, F; Barlow, M; De Looze, I; Sartorio, N (Monthly Notices of the Royal Astronomical Society)

Exploring the stellar populations of backsplash galaxies

Backsplash galaxies are those that traverse and overshoot cluster cores as they fall into these structures. They are affected by environment, and should stand out in contrast to the infalling population. We target galaxies in the vicinity of clusters (R ≳ R₂₀₀) and select a sample in projected phase space (PPS), from the compilation of Sampaio et al. based on the Sloan Digital Sky Survey data. We present a statistical analysis, comparing two regions in PPS, with the same projected distance to the cluster but different velocity. The analysis relies on the presence of variations in the stellar population content of backsplash galaxies. We find a lower limit in the fractional contribution of ~5 per cent with respect to the general sample of infalling galaxies at similar group-centric distance when using single line strength analysis, or ~15-30 per cent when adopting bivariate distributions. The stellar populations show a subtle but significant difference towards older ages, and a higher fraction of quiescent galaxies. We also compare this set with a general field sample, where a substantially larger difference in galaxy properties is found, with the field sample being consistently younger, metal poorer, and with a lower fraction of quiescent galaxies. Noting that our 'cluster' sample is located outside of the virial radius, we expect this difference to be caused by pre-processing of the infalling galaxies in the overall higher density regions.

January 2023: Ferreras, I; Bohm, A; Umetsu, K; Sampaio, V; de Carvalho, R (Monthly Notices of the Royal Astronomical Society)

Search for exotic physics in double-β decays with GERDA Phase II

A search for Beyond the Standard Model double-β decay modes of ⁷⁶Ge has been performed with data collected during the Phase II of the GERmanium Detector Array (GERDA) experiment, located at the Laboratori Nazionali del Gran Sasso of INFN (Italy). Improved limits on the decays involving Majorons have been obtained, compared to previous experiments with ⁷⁶Ge, with half-life values on the order of 10²³ yr. For the first time with ⁷⁶Ge, limits on Lorentz invariance violation effects in double-β decay have been obtained. The isotropic coefficient å_of⁽³⁾, which embeds Lorentz violation in double-β decay, has been constrained at the order of 10^-6 GeV. We also set the first experimental limits on the search for light exotic fermions in double-β decay, including sterile neutrinos.

December 2022: Agostini, M; Alexander, A; Araujo, G; Bakalyarov, A; Balata, M; et al. (Journal of Cosmology and Astroparticle Physics)

ExoMol line lists - XLVII. Rovibronic spectrum of aluminium monochloride (AlCl)

A line list for two isotopologues of aluminium monochloride, AlCl³⁵ and AlCl³⁷ are presented covering the wavelength range <0.2 μm, J up to 400 and applicable for temperatures up to 5000 K. The line lists are built using an empirical spectroscopic model consisting of potential energy curves, spin-orbit coupling curves, electronic angular momentum curves and Born-Oppenheimer Breakdown correction curves combined with ab initio dipole moments and covers the four lowest electronic states, X ¹Σ⁺, A ¹Π, a ³Π and b ³Σ⁺. Considerable problems with the assignments of some the laboratory rovibronic spectra are identified. Treatment of the states lying in the continuum is discussed. The YNAT line list is available from the ExoMol database at www.exomol.com.

December 2022: Yurchenko, S; Nogue, E; Azzam, A; Tennyson, J (Monthly Notices of the Royal Astronomical Society)

VarStar Detect: a Python library for the semi-automatic detection of stellar variability

VarStar Detect is a Python package available on PyPI optimized for the detection of variable stars using photometric measurements. Based on the method of the Least Squares regression, VarStar Detect calculates the amplitude of a trigonometric polynomial data fit as a measure of variability to assess whether the star is indeed variable. In this work, we present the mathematical background of the package and an analysis of the code's functionality based on TESS Sector 1 Data Release.

December 2022: Jorge, P; Nicolas, C; Andres, C (Advances in Astronomy and Space Physics)

Membrane nucleation rates from holography

Membrane nucleation, a higher dimensional analog of the Schwinger effect, is a useful toy model for vacuum decay. While a non-perturbative effect, the computation of nucleation rates has only been accomplished at weak coupling in the field theory. Here we compute the nucleation rates of spherical membranes using AdS/CFT duality, thus naturally including the effects of strong coupling. More precisely, we consider the nucleation of spherical membranes coupled to an antisymmetric tensor field, a process which renders the vacuum unstable above a critical value of the field strength. We analyze membrane creation in flat and de Sitter space using various foliations of AdS. This is accomplished via instanton methods, where the rate of nucleation is dominated by the semi-classical on-shell Euclidean action. Our findings generalize the holographic Schwinger effect and provide a step toward holographic false vacuum decay mediated by Coleman-De Luccia instantons.

December 2022: Arcos, M; Fischler, W; Pedraza, J; Svesko, A (Journal of High Energy Physics)

The recent star formation history of NGC 628 on resolved scales

Star formation histories (SFHs) are integral to our understanding of galaxy evolution. We can study recent SFHs by comparing the star formation rate (SFR) calculated using different tracers, as each probes a different time-scale. We aim to calibrate a proxy for the present-day rate of change in SFR, dSFR/dt, which does not require full spectral energy distribution (SED) modelling and depends on as few observables as possible, to guarantee its broad applicability. To achieve this, we create a set of models in CIGALE and define an SFR change diagnostic as the ratio of the SFR averaged over the past 5 and 200 Myr, $\langle SFR_{\rm {5}} \rangle \big / \langle SFR_{\rm {200}} \rangle$, probed by the H α-FUV colour. We apply $\langle SFR_{\rm {5}} \rangle \big / \langle SFR_{\rm {200}} \rangle$ to the nearby spiral NGC 628 and find that its star formation activity has overall been declining in the recent past, with the spiral arms, however, maintaining a higher level of activity. The impact of the spiral arm structure is observed to be stronger on $\langle SFR_{\rm {5}} \rangle \big / \langle SFR_{\rm {200}} \rangle$ than on the star formation efficiency. In addition, increasing disc pressure tends to increase recent star formation, and consequently $\langle SFR_{\rm {5}} \rangle \big / \langle SFR_{\rm {200}} \rangle$. We conclude that $\langle SFR_{\rm {5}} \rangle \big / \langle SFR_{\rm {200}} \rangle$ is sensitive to the molecular gas content, spiral arm structure, and disc pressure. The $\langle SFR_{\rm {5}} \rangle \big / \langle SFR_{\rm {200}} \rangle$ indicator is general and can be used to reconstruct the recent SFH of any star-forming galaxy for which H α, FUV, and either mid- or far-IR photometry is available, without the need of detailed modelling.

December 2022: Lomaeva, M; De Looze, I; Saintonge, A; Decleir, M (Monthly Notices of the Royal Astronomical Society)

Towards a better understanding of ice mantle desorption by cosmic rays

The standard model of cosmic ray heating-induced desorption of interstellar ices is based on a continuous representation of the sporadic desorption of ice mantle components from classical ($0.1\, \mu$m) dust grains. This has been re-evaluated and developed to include tracking the desorption through (extended) grain cooling profiles, consideration of grain size-dependencies and constraints to the efficiencies. A model was then constructed to study the true, sporadic, nature of the process with possible allowances from species co-desorption and whole mantle desorption from very small grains. The key results from the study are that the desorption rates are highly uncertain, but almost certainly significantly larger than have been previously determined. For typical interstellar grain size distributions it is found that the desorption is dominated by the contributions from the smallest grains. The sporadic desorption model shows that, if the interval between cosmic ray impacts is comparable to, or less than, the freeze-out time-scale, the continuous representation is inapplicable; chemical changes may occur on very long time-scales, resulting in strong gas phase chemical enrichments that have very non-linear dependences on the cosmic ray flux. The inclusion of even limited levels of species co-desorption and/or the contribution from very small grains further enhances the rates, especially for species such as H₂O. In general, we find that cosmic ray heating is the dominant desorption mechanism in dark environments. These results may have important chemical implications for protostellar and protoplanetary environments.

December 2022: Rawlings, J (Monthly Notices of the Royal Astronomical Society)

Stellar angular momentum can be controlled from cosmological initial conditions

The angular momentum of galaxies controls the kinematics of their stars, which in turn drives observable quantities such as the apparent radius, the bulge fraction, and the alignment with other nearby structures. To show how angular momentum of galaxies is determined, we build high (35 pc) resolution numerical experiments in which we increase or decrease the angular momentum of the Lagrangian patches in the early universe. We perform cosmological zoom-in simulations of three galaxies over their histories from z = 200 to z = 2, each with five different choices for the angular momentum (15 simulations in total). Our results show that altering early universe angular momentum changes the timing and orbital parameters of mergers, which in turn changes the total stellar angular momentum within a galaxy's virial radius in a predictable manner. Of our three galaxies, one has no large satellite at z = 2; in this case, the specific angular momentum is concentrated in the central galaxy. Our changes to the initial conditions result in its stellar angular momentum changing over 0.7 dex (from 61 to ${320}\, {\rm kpc\, km\, s}^{-1}$) at z = 2. This causes its effective radius to grow by 40 per cent, its v/σ parameter to grow by a factor of 2.6, and its bulge fraction to decrease from 0.72 to 0.57. This proof of concept illustrates how causal studies can contribute to a better understanding of the origin of galaxy scaling relations and intrinsic alignments.

December 2022: Cadiou, C; Pontzen, A; Peiris, H (Monthly Notices of the Royal Astronomical Society)

Internal quantum reference frames for finite Abelian groups

Employing internal quantum systems as reference frames is a crucial concept in quantum gravity, gauge theories, and quantum foundations whenever external relata are unavailable. In this work, we give a comprehensive and self-contained treatment of such quantum reference frames (QRFs) for the case when the underlying configuration space is a finite Abelian group, significantly extending our previous work [M. Krumm, P. A. Höhn, and M. P. Müller, Quantum 5, 530 (2021)]. The simplicity of this setup admits a fully rigorous quantum information–theoretic analysis, while maintaining sufficient structure for exploring many of the conceptual and structural questions also pertinent to more complicated setups. We exploit this to derive several important structures of constraint quantization with quantum information–theoretic methods and to reveal the relation between different approaches to QRF covariance. In particular, we characterize the "physical Hilbert space"—the arena of the "perspective-neutral" approach—as the maximal subspace that admits frame-independent descriptions of purifications of states. We then demonstrate the kinematical equivalence and, surprising, dynamical inequivalence of the "perspective-neutral" and the "alignability" approach to QRFs. While the former admits unitaries generating transitions between arbitrary subsystem relations, the latter, remarkably, admits no such dynamics when requiring symmetry-preservation. We illustrate these findings by example of interacting discrete particles, including how dynamics can be described "relative to one of the subystems."

November 2022: Hohn, P; Krumm, M; Muller, M (Journal of Mathematical Physics)

Mira variables in the Milky Way's nuclear stellar disc: discovery and classification

The properties of the Milky Way's nuclear stellar disc give crucial information on the epoch of bar formation. Mira variables are promising bright candidates to study the nuclear stellar disc, and through their period-age relation dissect its star formation history. We report on a sample of 1782 Mira variable candidates across the central $3\times 3\, \mathrm{deg}^2$ of the Galaxy using the multi-epoch infrared VISTA Variables in Via Lactea (VVV) survey. We describe the algorithms employed to select candidate variable stars and then model their light curves using periodogram and Gaussian process methods. By combining with WISE, 2MASS, and other archival photometry, we model the multiband light curves to refine the periods and inspect the amplitude variation between different photometric bands. The infrared brightness of the Mira variables means many are too bright and missed by VVV. However, our sample follows a well-defined selection function as expected from artificial star tests. The multiband photometry is modelled using stellar models with circumstellar dust that characterize the mass-loss rates. We demonstrate how ≳90 per cent of our sample is consistent with O-rich chemistry. Comparison to period-luminosity relations demonstrates that the bulk of the short period stars are situated at the Galactic Centre distance. Many of the longer period variables are very dusty, falling significantly under the O-rich Magellanic Cloud and solar neighbourhood period-luminosity relations and exhibit high mass-loss rates of $\sim 2.5\times 10^{-5}M_\odot \, \mathrm{yr}^{-1}$. The period distribution appears consistent with the nuclear stellar disc forming $\gtrsim 8\, \mathrm{Gyr}$ ago, although it is not possible to disentangle the relative contributions of the nuclear stellar disc and the contaminating bulge.

November 2022: Sanders, J; Matsunaga, N; Kawata, D; Smith, L; Minniti, D; et al. (Monthly Notices of the Royal Astronomical Society)

Galaxy and Mass Assembly (GAMA): probing galaxy-group correlations in redshift space with the halo streaming model

We have studied the galaxy-group cross-correlations in redshift space for the Galaxy And Mass Assembly (GAMA) Survey. We use a set of mock GAMA galaxy and group catalogues to develop and test a novel 'halo streaming' model for redshift-space distortions. This treats 2-halo correlations via the streaming model, plus an empirical 1-halo term derived from the mocks, allowing accurate modelling into the non-linear regime. In order to probe the robustness of the growth rate inferred from redshift-space distortions, we divide galaxies by colour, and divide groups according to their total stellar mass, calibrated to total mass via gravitational lensing. We fit our model to correlation data, to obtain estimates of the perturbation growth rate, fσ₈, validating parameter errors via the dispersion between different mock realizations. In both mocks and real data, we demonstrate that the results are closely consistent between different subsets of the group and galaxy populations, considering the use of correlation data down to some minimum projected radius, r_min. For the mock data, we can use the halo streaming model to below $r_{\rm min} = 5{\, h^{-1}\, \rm Mpc}$, finding that all subsets yield growth rates within about 3 per cent of each other, and consistent with the true value. For the actual GAMA data, the results are limited by cosmic variance: fσ₈ = 0.29 ± 0.10 at an effective redshift of 0.20; but there is every reason to expect that this method will yield precise constraints from larger data sets of the same type, such as the Dark Energy Spectroscopic Instrument (DESI) bright galaxy survey.

November 2022: Hang, Q; Peacock, J; Alam, S; Cai, Y; Kraljic, K; et al. (Monthly Notices of the Royal Astronomical Society)

Identifying the most constraining ice observations to infer molecular binding energies

In order to understand grain-surface chemistry, one must have a good understanding of the reaction rate parameters. For diffusion-based reactions, these parameters are binding energies of the reacting species. However, attempts to estimate these values from grain-surface abundances using Bayesian inference are inhibited by a lack of enough sufficiently constraining data. In this work, we use the Massive Optimised Parameter Estimation and Data compression algorithm to determine which species should be prioritized for future ice observations to better constrain molecular binding energies. Using the results from this algorithm, we make recommendations for which species future observations should focus on.

November 2022: Heyl, J; Sellentin, E; Holdship, J; Viti, S (Monthly Notices of the Royal Astronomical Society)

Strong C IV emission from star-forming galaxies: a case for high Lyman continuum photon escape

Finding reliable indicators of Lyman continuum (Ly C) photon leakage from galaxies is essential in order to infer their escape fraction in the epoch of reionization, where direct measurements of Ly C flux are impossible. To this end, here we investigate whether strong C IV λλ1548, 1550 emission in the rest-frame UV spectra of galaxies traces conditions ripe for ample production and escape of Ly C photons. We compile a sample of 19 star-forming galaxies in the redshift range $z$ = 3.1-4.6 from the VANDELS survey that exhibit strong C IV emission, producing a stacked spectrum where all major rest-UV emission lines are clearly detected. Best-fitting spectral energy distribution models containing both stellar and nebular emission suggest the need for low stellar metallicities ($Z=0.1--0.2\, Z_\odot$), young stellar ages ($\log (\rm {age\,yr^{-1}}) = 6.1--6.5$), a high ionization parameter (log U = -2) and little to no dust attenuation (E(B - V) = 0.00-0.01). However, these models are unable to fully reproduce the observed C IV and He II line strengths. We find that the Ly α line in the stacked spectrum is strong and peaks close to the systemic velocity, features that are indicative of significant Ly C photon leakage along the line of sight. The covering fractions of low-ionization interstellar absorption lines are also low, implying Ly C escape fraction in the range ≈0.05-0.30, with signatures of outflowing gas. Finally, C IV/C III] ratios of >0.75 for a subset of individual galaxies with reliable detections of both lines are also consistent with physical conditions that enable significant Ly C leakage. Overall, we report that multiple spectroscopic indicators of Ly C leakage are present in the stacked spectrum of strong C IV emitting galaxies, potentially making C IV an important tracer of Ly C photon escape at $z$ > 6.

November 2022: Saxena, A; Cryer, E; Ellis, R; Pentericci, L; Calabro, A; et al. (Monthly Notices of the Royal Astronomical Society)

ExoMol line lists - XLVII. Rovibronic molecular line list of the calcium monohydroxide radical (CaOH)

Any future detection of the calcium monohydroxide radical (CaOH) in stellar and exoplanetary atmospheres will rely on accurate molecular opacity data. Here, we present the first comprehensive molecular line list of CaOH covering the $\tilde{A}\, ^2\Pi$-$\tilde{X}\, ^2\Sigma ^+$ rotation-vibration-electronic and $\tilde{X}\, ^2\Sigma ^+$-$\tilde{X}\, ^2\Sigma ^+$ rotation-vibration bands. The newly computed OYT6 line list contains over 24.2 billion transitions between 3.2 million energy levels with rotational excitation up to J = 175.5. It is applicable to temperatures up to T = 3000 K and covers the 0-35 000 cm^-1 range (wavelengths λ > 0.29 μm) for rotational, rotation-vibration and the $\tilde{A}\, ^2\Pi$-$\tilde{X}\, ^2\Sigma ^+$ electronic transitions. The strong band around 16 000 cm^-1 (λ = 0.63 μm) is likely to be of interest in future astronomical observations, particularly in hot rocky exoplanets where temperatures can become extremely high. The OYT6 line list has been generated using empirically refined $\tilde{X}\, ^2\Sigma ^+$ and $\tilde{A}\, ^2\Pi$ state potential energy surfaces, high-level ab initio transition dipole moment surfaces, and a rigorous treatment of both Renner-Teller and spin-orbit coupling effects, which are necessary for correctly modelling the CaOH spectrum. Post-processing of the CaOH line list has been performed so as to tailor it to high-resolution applications, i.e. by replacing calculated energy levels with more accurate empirically derived values (where available), hence improving the accuracy of the predicted line positions in certain regions. The OYT6 line list is available from the ExoMol data base at www.exomol.com and the CDS astronomical data base.

November 2022: Owens, A; Mitrushchenkov, A; Yurchenko, S; Tennyson, J (Monthly Notices of the Royal Astronomical Society)

ExoMol line lists - XLVI. Empirical rovibronic spectra of silicon mononitrate (SiN) covering the six lowest electronic states and four isotopologues

Silicon mononitride (²⁸Si¹⁴N, ²⁹Si¹⁴N, ³⁰Si¹⁴N, ²⁸Si¹⁵N) line lists covering infrared, visible, and ultraviolet regions are presented. The SiNful line lists produced by ExoMol include rovibronic transitions between six electronic states: $X\, {}^{2}\Sigma ^{+}$, $A\, {}^{2}\Pi$, $B\, {}^{2}\Sigma ^{+}$, $D\, {}^{2}\Delta$, $a\, {}^{4}\Sigma ^{+}$, $b\, {}^{4}\Pi$. The ab initio potential energy and coupling curves, computed at the multireference configuration interaction (MRCI/aug-cc-pVQZ) level of theory, are refined for the observed states by fitting their analytical representations to 1052 experimentally derived SiN energy levels determined from rovibronic bands belonging to the X-X, A-X, and B-X electronic systems through the MARVEL procedure. The SiNful line lists are compared to previously observed spectra, recorded and calculated lifetimes, and previously calculated partition functions. SiNful is available via the www.exomol.com database.

October 2022: Semenov, M; Clark, N; Yurchenko, S; Kim, G; Tennyson, J (Monthly Notices of the Royal Astronomical Society)

Three-point intrinsic alignments of dark matter haloes in the IllustrisTNG simulation

We use the IllustrisTNG suite of cosmological simulations to measure intrinsic alignment (IA) bispectra of dark matter subhaloes between redshifts 0 and 1. We decompose the intrinsic shear field into E- and B- modes and find that the bispectra B_δδE and B_δEE, between the matter overdensity field, δ, and the E-mode field, are detected with high significance. We also model the IA bispectra analytically using a method consistent with the two-point non-linear alignment model. We use this model and the simulation measurements to infer the IA amplitude A_IA and find that values of A_IA obtained from IA power spectra and bispectra agree well at scales up to $k_\mathrm{max}= 2 \, h \mathrm{Mpc}^{-1}$. For example at z = 1, A_IA = 2.13 ± 0.02 from the cross power spectrum between the matter overdensity and E-mode fields and A_IA = 2.11 ± 0.03 from B_δδE. This demonstrates that a single physically motivated model can jointly model two-point and three-point statistics of IAs, thus enabling a cleaner separation between IAs and cosmological weak lensing signals.

October 2022: Pyne, S; Tenneti, A; Joachimi, B (Monthly Notices of the Royal Astronomical Society)

Stellar wind properties of the nearly complete sample of O stars in the low metallicity young star cluster NGC 346 in the SMC galaxy

Context. Massive stars are among the main cosmic engines driving the evolution of star-forming galaxies. Their powerful ionising radiation and stellar winds inject a large amount of energy in the interstellar medium. Furthermore, mass-loss (Ṁ) through radiatively driven winds plays a key role in the evolution of massive stars. Even so, the wind mass-loss prescriptions used in stellar evolution models, population synthesis, and stellar feedback models often disagree with mass-loss rates empirically measured from the UV spectra of low metallicity massive stars.
Aims: The most massive young star cluster in the low metallicity Small Magellanic Cloud galaxy is NGC 346. This cluster contains more than half of all O stars discovered in this galaxy so far. A similar age, metallicity (Z), and extinction, the O stars in the NGC 346 cluster are uniquely suited for a comparative study of stellar winds in O stars of different subtypes. We aim to use a sample of O stars within NGC 346 to study stellar winds at low metallicity.
Methods: We mapped the central 1' of NGC 346 with the long-slit UV observations performed by the Space Telescope Imaging Spectrograph (STIS) on board of the Hubble Space Telescope and complemented these new datasets with archival observations. Multi-epoch observations allowed for the detection of wind variability. The UV dataset was supplemented by optical spectroscopy and photometry. The resulting spectra were analysed using a non-local thermal equilibrium model atmosphere code (PoWR) to determine wind parameters and ionising fluxes.
Results: The effective mapping technique allowed us to obtain a mosaic of almost the full extent of the cluster and resolve stars in its core. Among hundreds of extracted stellar spectra, 21 belong to O stars. Nine of them are classified as O stars for the first time. We analyse, in detail, the UV spectra of 19 O stars (with a further two needing to be analysed in a later paper due to the complexity of the wind lines as a result of multiplicity). This more than triples the number of O stars in the core of NGC 346 with constrained wind properties. We show that the most commonly used theoretical mass-loss recipes for O stars over-predict mass-loss rates. We find that the empirical scaling between mass-loss rates (Ṁ) and luminosity (L), Ṁ ∝ L^2.4, is steeper than theoretically expected by the most commonly used recipes. In agreement with the most recent theoretical predictions, we find within Ṁ ∝ Z^α that α is dependent upon L. Only the most luminous stars dominate the ionisation feedback, while the weak stellar winds of O stars in NGC 346 and the lack of previous supernova explosions in this cluster restrict the kinetic energy input.

October 2022: Rickard, M; Hainich, R; Hamann, W; Oskinova, L; Prinja, R; et al. (Astronomy and Astrophysics)

Radial velocities from far-red spectra of Carina Arm O and early B stars

Massive O and early B stars are important markers of recent star formation and exert a significant influence on their environments during their short lives via photoionization and winds and when they explode as supernovae. In the Milky Way, they can be detected at great distances but often lie behind large dust columns, making detection at short wavelengths difficult. In this study, the use of the less extinguished far-red spectrum (8400-8800 Å) for radial velocity measurement is examined. Results are reported for a sample of 164 confirmed OB stars within a 2° field positioned on the Carina Arm. Most stars are at distances between 3 and 6 kpc, and Westerlund 2 is at the field edge. The measured radial velocities have errors concentrated in the 3-10 km s^-1 range, with a systematic uncertainty of 2-3 km s^-1. These are combined with Gaia-mission astrometry to allow full space motions to be constructed. Up to 22 stars are likely to be runaways, although 8 of them are as likely to be interloping (so far undetected) binaries. The mean azimuthal motion of the sample fits in with recent measurements of Galactic disc rotation. In the Galactocentric radial direction, the mean motion indicates modest infall at a speed of ~10 km s^-1. This experiment shows that weak Paschen lines in the far-red can yield credible radial velocity determination, offering the prospect of exploring OB-star kinematics over much more of the Galactic disc than has hitherto been possible.

October 2022: Drew, J; Blake-Parsons, F; Mohr-Smith, M (Monthly Notices of the Royal Astronomical Society)

Robust sampling for weak lensing and clustering analyses with the dark energy survey

Recent cosmological analyses rely on the ability to accurately sample from high-dimensional posterior distributions. A variety of algorithms have been applied in the field, but justification of the particular sampler choice and settings is often lacking. Here we investigate three such samplers to motivate and validate the algorithm and settings used for the Dark Energy Survey (DES) analyses of the first 3 years (Y3) of data from combined measurements of weak lensing and galaxy clustering. We employ the full DES Year 1 likelihood alongside a much faster approximate likelihood, which enables us to assess the outcomes from each sampler choice and demonstrate the robustness of our full results. We find that the ellipsoidal nested sampling algorithm MultiNest reports inconsistent estimates of the Bayesian evidence and somewhat narrower parameter credible intervals than the sliced nested sampling implemented in PolyChord. We compare the findings from MultiNest and PolyChord with parameter inference from the Metropolis-Hastings algorithm, finding good agreement. We determine that PolyChord provides a good balance of speed and robustness for posterior and evidence estimation, and recommend different settings for testing purposes and final chains for analyses with DES Y3 data. Our methodology can readily be reproduced to obtain suitable sampler settings for future surveys.

October 2022: Lemos, P; Weaverdyck, N; Rollins, R; Muir, J; Ferte, A; et al. (Monthly Notices of the Royal Astronomical Society)

Spore Survival During Abrasive Saltation on Mars: A Comment on Bak et al.

In original experiments, Bak et al. (Wind-Driven Saltation: An Overlooked Challenge for Life on Mars. Astrobiology 2019;19(4):497-505) suggest a new mechanism for the destruction of spores on Mars: abrasion by wind-driven saltation. Bak et al. found that the tumbling of spores on grain surfaces (simulating saltation) was, by far, most lethal at the outset of their experiments. They suggest that it may be sharp edges of the freshly crushed basalt particles used in their experiments that destroy the spores and that these edges abrade away over the course of each experiment. But prior Mars analogue experiments, observations of particles from terrestrial deserts, and imaging from Mars landers suggest that most martian dust has been rounded by billions of years of aeolian processes. If so, saltation on Mars is more likely well simulated by the later stages of the Bak et al. experiments, reducing implied lethality by orders of magnitude. Experiments could test this by beginning with particles that had been already abraded. Even assuming the highest lethality found in their experiments, saltation "hop" distances on Mars suggest that abrasion would not prevent ∼1% of released spores from remaining viable while traveling hundreds or even thousands of kilometers.

September 2022: Minns, C; Louden, E; Chyba, C (Astrobiology)

Weak-lensing magnification of Type Ia supernovae from the Pantheon sample

Using data from the Pantheon Type Ia supernovae (SN Ia) compilation and the Sloan Digital Sky Survey, we propose an estimator for weak-lensing convergence incorporating positional and photometric data of foreground galaxies. The correlation between this and the Hubble diagram residuals of the supernovae has 3.6σ significance, and is consistent with weak-lensing magnification due to dark matter haloes centred on galaxies. We additionally constrain the properties of the galactic haloes, such as the mass-to-light ratio Γ and radial profile of the halo matter density ρ(r). We derive a new relationship for the additional rms scatter in magnitudes caused by lensing, finding σ_lens = (0.06 ± 0.017)(d_C(z)/d_C(z = 1))^3/2, where d_C(z) is the comoving distance to redshift z. Hence, the scatter in apparent magnitudes due lensing will be of the same size as the intrinsic scatter of SN Ia by z ~ 1.2. We propose a modification of the distance modulus estimator for SN Ia to incorporate lensing, which can be easily calculated from observational data. We anticipate this will improve the accuracy of cosmological parameter estimation for high-redshift SN Ia data.

September 2022: Shah, P; Lemos, P; Lahav, O (Monthly Notices of the Royal Astronomical Society)

Magnetic fields and outflows in the large Bok globule CB 54

We have observed the large Bok globule CB 54 in 850-$\mu$m polarized light using the POL-2 polarimeter on the James Clerk Maxwell Telescope (JCMT). We find that the magnetic field in the periphery of the globule shows a significant, ordered deviation from the mean-field direction in the globule centre. This deviation appears to correspond with the extended but relatively weak ¹²CO outflow emanating from the Class 0 sources at the centre of the globule. Energetics analysis suggests that if the outflow is reshaping the magnetic field in the globule's periphery, then we can place an upper limit of $\lt 27\, \mu$G on the magnetic field strength in the globule's periphery. Comparison with archival Planck and CARMA measurements shows that the field in the centre of the globule is consistent over several orders of magnitude in size scale, and oriented parallel to the density structure in the region in projection. We thus hypothesize that while non-thermal motions in the region may be sub-Alfvénic, the magnetic field is subdominant to gravity over a wide range of size scales. Our results suggest that even a relatively weak outflow may be able to significantly reshape magnetic fields in star-forming regions on scales >0.1 pc.

September 2022: Pattle, K; Lai, S; Sadavoy, S; Coude, S; Wolf, S; et al. (Monthly Notices of the Royal Astronomical Society)

KiDS and Euclid: Cosmological implications of a pseudo angular power spectrum analysis of KiDS-1000 cosmic shear tomography

We present a tomographic weak lensing analysis of the Kilo Degree Survey Data Release 4 (KiDS-1000), using a new pseudo angular power spectrum estimator (pseudo-C_ℓ) under development for the ESA Euclid mission. Over 21 million galaxies with shape information are divided into five tomographic redshift bins, ranging from 0.1 to 1.2 in photometric redshift. We measured pseudo-C_ℓ using eight bands in the multipole range 76 < ℓ < 1500 for auto- and cross-power spectra between the tomographic bins. A series of tests were carried out to check for systematic contamination from a variety of observational sources including stellar number density, variations in survey depth, and point spread function properties. While some marginal correlations with these systematic tracers were observed, there is no evidence of bias in the cosmological inference. B-mode power spectra are consistent with zero signal, with no significant residual contamination from E/B-mode leakage. We performed a Bayesian analysis of the pseudo-C_ℓ estimates by forward modelling the effects of the mask. Assuming a spatially flat ΛCDM cosmology, we constrained the structure growth parameter S₈ = σ₈(Ω_m/0.3)^1/2 = 0.754_−0.029^+0.027. When combining cosmic shear from KiDS-1000 with baryon acoustic oscillation and redshift space distortion data from recent Sloan Digital Sky Survey (SDSS) measurements of luminous red galaxies, as well as the Lyman-α forest and its cross-correlation with quasars, we tightened these constraints to S₈ = 0.771_−0.032^+0.006. These results are in very good agreement with previous KiDS-1000 and SDSS analyses and confirm a ∼3σ tension with early-Universe constraints from cosmic microwave background experiments.

September 2022: Loureiro, A; Whittaker, L; Spurio Mancini, A; Joachimi, B; Cuceu, A; et al. (Astronomy and Astrophysics)

Dust masses for a large sample of core-collapse supernovae from optical emission line asymmetries: dust formation on 30-year time-scales

Modelling the red-blue asymmetries seen in the broad emission lines of core-collapse supernovae (CCSNe) is a powerful technique to quantify total dust mass formed in the ejecta at late times (>5 yr after outburst) when ejecta dust temperatures become too low to be detected by mid-infrared (IR) instruments. Following our success in using the Monte Carlo radiative transfer code DAMOCLES to measure the dust mass evolution in SN 1987A and other CCSNe, we present the most comprehensive sample of dust mass measurements yet made with DAMOCLES, for CCSNe aged between 4 and 60 yr after outburst. Our sample comprises multi-epoch late-time optical spectra taken with the Gemini/Gemini Multi-Object Spectrographs (GMOS) and Very Large Telescope (VLT) X-Shooter spectrographs, supplemented by archival spectra. For the 14 CCSNe that we have modelled, we confirm a dust mass growth with time that can be fit by a sigmoid curve that is found to saturate beyond an age of ~30 yr, at a mass of 0.23$^{+0.17}_{-0.12}$ M_⊙. For an expanded sample including dust masses found in the literature for a further 11 CCSNe and six CCSN remnants, the dust mass at saturation is found to be 0.42$^{+0.09}_{-0.05}$ M_⊙. Uncertainty limits for our dust masses were determined from a Bayesian analysis using the affine invariant Markov chain Monte Carlo ensemble sampler EMCEE with DAMOCLES. The best-fitting line profile models for our sample all required grain radii between 0.1 and 0.5 $\mu$m. Our results are consistent with CCSNe forming enough dust in their ejecta to significantly contribute to the dust budget of the Universe.

September 2022: Niculescu-Duvaz, M; Barlow, M; Bevan, A; Wesson, R; Milisavljevic, D; et al. (Monthly Notices of the Royal Astronomical Society)

Galaxy mergers can initiate quenching by unlocking an AGN-driven transformation of the baryon cycle

We use zoom simulations to show how merger-driven disruption of the gas disc in a galaxy provides its central active galactic nucleus (AGN) with fuel to drive outflows that entrain and expel a significant fraction of the circumgalactic medium (CGM). This in turn suppresses replenishment of the interstellar medium, causing the galaxy to quench up to several Gyr after the merger. We start by performing a zoom simulation of a present-day star-forming disc galaxy with the EAGLE galaxy formation model. Then, we re-simulate the galaxy with controlled changes to its initial conditions, using the genetic modification technique. These modifications either increase or decrease the stellar mass ratio of the galaxy's last significant merger, which occurs at $z$ ≈ 0.74. The halo reaches the same present-day mass in all cases, but changing the mass ratio of the merger yields markedly different galaxy and CGM properties. We find that a merger can unlock rapid growth of the central supermassive black hole if it disrupts the co-rotational motion of gas in the black hole's vicinity. Conversely, if a less disruptive merger occurs and gas close to the black hole is not disturbed, the AGN does not strongly affect the CGM, and consequently the galaxy continues to form stars. Our result illustrates how a unified view of AGN feedback, the baryon cycle and the interstellar medium is required to understand how mergers and quenching are connected over long time-scales.

September 2022: Davies, J; Pontzen, A; Crain, R (Monthly Notices of the Royal Astronomical Society)

A variational model for the hyperfine resolved spectrum of VO in its ground electronic state

A variational model for the infra-red spectrum of vanadium monoxide (VO) is presented, which aims to accurately predict the hyperfine structure within the VO XΣ-4 electronic ground state. To give the correct electron spin splitting of the XΣ-4 state, electron spin dipolar interaction within the ground state and the spin-orbit coupling between XΣ-4 and two excited states, AΠ4 and 1Σ+2, are calculated ab initio alongside hyperfine interaction terms. Four hyperfine coupling terms are explicitly considered: Fermi-contact interaction, electron spin-nuclear spin dipolar interaction, nuclear spin-rotation interaction, and nuclear electric quadrupole interaction. These terms are included as part of a full variational solution of the nuclear-motion Schrödinger equation performed using program DUO, which is used to generate both hyperfine-resolved energy levels and spectra. To improve the accuracy of the model, ab initio curves are subject to small shifts. The energy levels generated by this model show good agreement with the recently derived empirical term values. This and other comparisons validate both our model and the recently developed hyperfine modules in DUO.

September 2022: Qu, Q; Yurchenko, S; Tennyson, J (Journal of Chemical Physics)

Quasi-local energy and microcanonical entropy in two-dimensional nearly de Sitter gravity

We study the semi-classical thermodynamics of two-dimensional de Sitter space (dS₂) in Jackiw-Teitelboim (JT) gravity coupled to conformal matter. We extend the quasi-local formalism of Brown and York to dS₂, where a timelike boundary is introduced in the static patch to uniquely define conserved charges, including quasi-local energy. The boundary divides the static patch into two systems, a cosmological system and a black hole system, the former being unstable under thermal fluctuations while the latter is stable. A semi-classical quasi-local first law is derived, where the Gibbons-Hawking entropy is replaced by the generalized entropy. In the microcanonical ensemble the generalized entropy is stationary. Further, we show the on-shell Euclidean microcanonical action of a causal diamond in semi-classical JT gravity equals minus the generalized entropy of the diamond, hence extremization of the entropy follows from minimizing the action. Thus, we provide a first principles derivation of the island rule for U(1) symmetric dS₂ backgrounds, without invoking the replica trick. We discuss the implications of our findings for static patch de Sitter holography.

August 2022: Svesko, A; Verheijden, E; Verlinde, E; Visser, M (Journal of High Energy Physics)

Gravitational torques dominate the dynamics of accreted gas at z > 2

Galaxies form from the accretion of cosmological infall of gas. In the high redshift Universe, most of this gas infall is expected to be dominated by cold filamentary flows which connect deep down inside haloes, and, hence, to the vicinity of galaxies. Such cold flows are important since they dominate the mass and angular momentum acquisition that can make up rotationally-supported discs at high-redshifts. We study the angular momentum acquisition of gas into galaxies, and in particular, the torques acting on the accretion flows, using hydrodynamical cosmological simulations of high-resolution zoomed-in haloes of a few $10^{11}\, \rm M_\odot$ at z = 2. Torques can be separated into those of gravitational origin, and hydrodynamical ones driven by pressure gradients. We find that coherent gravitational torques dominate over pressure torques in the cold phase, and are hence responsible for the spin-down and realignment of this gas. Pressure torques display small-scale fluctuations of significant amplitude, but with very little coherence on the relevant galaxy or halo-scale that would otherwise allow them to effectively re-orientate the gas flows. Dark matter torques dominate gravitational torques outside the galaxy, while within the galaxy, the baryonic component dominates. The circum-galactic medium emerges as the transition region for angular momentum re-orientation of the cold component towards the central galaxy's mid-plane.

August 2022: Cadiou, C; Dubois, Y; Pichon, C (Monthly Notices of the Royal Astronomical Society)

The BINGO project. V. Further steps in component separation and bispectrum analysis

Context. Observing the neutral hydrogen distribution across the Universe via redshifted 21 cm line intensity mapping constitutes a powerful probe for cosmology. However, the redshifted 21 cm signal is obscured by the foreground emission from our Galaxy and other extragalactic foregrounds. This paper addresses the capabilities of the BINGO survey to separate such signals.
Aims: We show that the BINGO instrumental, optical, and simulations setup is suitable for component separation, and that we have the appropriate tools to understand and control foreground residuals. Specifically, this paper looks in detail at the different residuals left over by foreground components, shows that a noise-corrected spectrum is unbiased, and shows that we understand the remaining systematic residuals by analyzing nonzero contributions to the three-point function.
Methods: We use the generalized needlet internal linear combination, which we apply to sky simulations of the BINGO experiment for each redshift bin of the survey. We use binned estimates of the bispectrum of the maps to assess foreground residuals left over after component separation in the final map.
Results: We present our recovery of the redshifted 21 cm signal from sky simulations of the BINGO experiment, including foreground components. We test the recovery of the 21 cm signal through the angular power spectrum at different redshifts, as well as the recovery of its non-Gaussian distribution through a bispectrum analysis. We find that non-Gaussianities from the original foreground maps can be removed down to, at least, the noise limit of the BINGO survey with such techniques.
Conclusions: Our component separation methodology allows us to subtract the foreground contamination in the BINGO channels down to levels below the cosmological signal and the noise, and to reconstruct the 21 cm power spectrum for different redshift bins without significant loss at multipoles 20 ≲ ℓ ≲ 500. Our bispectrum analysis yields strong tests of the level of the residual foreground contamination in the recovered 21 cm signal, thereby allowing us to both optimize and validate our component separation analysis.

August 2022: Fornazier, K; Abdalla, F; Remazeilles, M; Vieira, J; Marins, A; et al. (Astronomy and Astrophysics)

EXOMOL photodissociation cross-sections - I. HCl and HF

Photon initiated chemistry, i.e. the interaction of light with chemical species, is a key factor in the evolution of the atmosphere of exoplanets. For planets orbiting stars in UV-rich environments, photodissociation induced by high-energy photons dominates the atmosphere composition and dynamics. The rate of photodissociation can be highly dependent on atmospheric temperature, as increased temperature leads to increased population of vibrational excited states and the consequent lowering of the photodissociation threshold. This paper inaugurates a new series of papers presenting computed temperature-dependent photodissociation cross-sections with rates generated for different stellar fields. Cross-sections calculations are performed by solving the time-independent Schrödinger equation for each electronic state involved in the process. Here, photodissociation cross-sections for hydrogen chloride and hydrogen fluoride are computed for a grid of 34 temperatures between 0 and 10 000 K. Use of different radiation fields shows that for the Sun and cooler stars the photodissociation rate can increase exponentially for molecular temperatures above 1000 K; conversely the photodissociation rates in UV rich fields instead are almost insensitive to the temperature of the molecule. Furthermore, these rates show extreme sensitivity to the radiation model used for cool stars, suggesting that further work on these may be required. The provision of an ExoMol data base of cross-sections is discussed.

August 2022: Pezzella, M; Tennyson, J; Yurchenko, S (Monthly Notices of the Royal Astronomical Society)

The extinction law in the inner 3 × 3 deg² of the Milky Way and the red clump absolute magnitude in the inner bar-bulge

The extinction law from 0.9 to 8 microns in the inner $3\times 3\deg ^2$ of the Milky Way is measured using data from VISTA Variables in the Via Lactea, GLIMPSE, and WISE. Absolute extinction ratios are found by requiring that the observed red clump density peaks at the GRAVITY collaboration distance to the Galactic centre. When combined with selective extinction ratios measured from the bulge giant colour-colour diagrams, we find an extinction law of $A_Z:A_Y:A_J:A_H:A_{K_s}:A_{W1}:A_{[3.6]}:A_{[4.5]}:A_{W2}:A_{[5.8]}:A_{[8.0]} =7.19(0.30):5.11(0.20):3.23(0.11):1.77(0.04):1:0.54(0.02):0.46(0.03):0.34(0.03):0.32(0.03):0.24(0.04):0.28(0.03)$ valid for low extinctions where non-linearities are unimportant. These results imply an extinction law from the Rayleigh Jeans colour excess method of $A_{K_s}=0.677(H-[4.5]-0.188)$. We find little evidence for significant selective extinction ratio variation over the inspected region (around $5\, \mathrm{per\, cent}$). Assuming the absolute extinction ratios do not vary across the inspected region gives an independent measurement of the absolute K_s magnitude of the red clump at the Galactic Centre of $(-1.61\pm 0.07)\, \mathrm{mag}$. This is very similar to the value measured for solar neighbourhood red clump stars giving confidence in the use of red clump stars as standard candles across the Galaxy. As part of our analysis, we inspect the completeness of PSF photometry from the VVV survey using artificial star tests, finding $90\, \mathrm{per\, cent}$ completeness at $K_s\approx 16 \, (17)$ in high (low) density regions and good agreement with the number counts with respect to the GALACTICNUCLEUS and DECAPS catalogues over small regions of the survey.

August 2022: Sanders, J; Smith, L; Gonzalez-Fernandez, C; Lucas, P; Minniti, D (Monthly Notices of the Royal Astronomical Society)

The BINGO Project. III. Optical design and optimization of the focal plane

Context. The Baryon Acoustic Oscillations from Integrated Neutral Gas Observations (BINGO) telescope was designed to measure the fluctuations of the 21 cm radiation arising from the hyperfine transition of neutral hydrogen. It is also aimed at measuring the baryon acoustic oscillations (BAO) from such fluctuations, thereby serving as a pathfinder to future, deeper intensity mapping surveys. The requirements for the Phase 1 of the projects consider a large reflector system (two 40 m-class dishes in a crossed-Dragone configuration) illuminating a focal plane with 28 horns to measure the sky, with two circular polarizations in a drift scan mode to produce measurements of the radiation in intensity (I) as well as the circular (V) polarization.
Aims: In this paper, we present the optical design for the instrument. We describe the optical arrangement of the horns in the focal plane to produce a homogeneous and well-sampled map after the end of Phase 1, as well as the intensity and polarization properties of the beams. Our analysis provides an optimal model for the location of the horns in the focal plane, producing a homogeneous and Nyquist-sampled map after the nominal survey time.
Methods: We used the GRASP package to model the focal plane arrangement and performed several optimization tasks to arrive at the current configuration, including an estimation of the sidelobes corresponding to the diffraction patterns of the two mirrors. The final model for the focal plane was defined through a combination of neural network and other direct optimization methods.
Results: We arrived at an optimal configuration for the optical system that includes the focal plane positioning and the beam behavior of the instrument. We present an estimate of the expected sidelobes both for intensity and polarization, as well as the effect of band averaging on the final sidelobes, as well as an estimation of the cross-polarization leakage for the final configuration.
Conclusions: We conclude that the chosen optical design meets the requirements for the project in terms of polarization purity and area coverage as well as a homogeneity of coverage so that BINGO can perform a successful BAO experiment. We further conclude that the requirements on the placement and rms error on the mirrors are also achievable so that a successful experiment can be conducted.

August 2022: Abdalla, F; Marins, A; Motta, P; Abdalla, E; Ribeiro, R; et al. (Astronomy and Astrophysics)

Entanglement based tomography to probe new macroscopic forces

Quantum entanglement provides a novel way to test short distance physics in the nonrelativistic regime. We will provide a protocol to potentially test new physics by bringing two charged massive particle interferometers adjacent to each other. Being charged, the two superpositions will be entangled via electromagnetic interactions mediated by the photons, including the Coulomb and the Casimir-Polder potential. We will bring a method of entanglement based tomography to seek time evolution of very small entanglement phases to probe new physical effects mediated by hitherto unknown macroscopic force which might be responsible for entangling the two charged superpositions modeled by the Yukawa type potential. We will be able to constrain the Yukawa couplings α ≥10^-35 for r ≥10^-6 m for new physics occurring in the electromagnetic sector, and in the gravitational potential α_g≥10^-8 for r ≥10^-6 m . Furthermore, our protocol can also constrain the axionlike particle mass and coupling, which is complimentary to the existing experimental bounds.

August 2022: Barker, P; Bose, S; Marshman, R; Mazumdar, A (Physical Review D)

The Cold Interstellar Medium of Galaxies in the Local Universe

The cold interstellar medium (ISM) plays a central role in the galaxy evolution process. It is the reservoir that fuels galaxy growth via star formation, the repository of material formed by these stars, and a sensitive tracer of internal and external processes that affect entire galaxies. Consequently, significant efforts have gone into systematic surveys of the cold ISM of the galaxies in the local Universe. This review discusses the resulting network of scaling relations connecting the atomic and molecular gas masses of galaxies with their other global properties (stellar masses, morphologies, metallicities, star-formation activity…) and their implications for our understanding of galaxy evolution. Key take-home messages are as follows: From a gas perspective, there are three main factors that determine the star-formation rate of a galaxy: the total mass of its cold ISM, how much of that gas is molecular, and the rate at which any molecular gas is converted into stars. All three of these factors vary systematically across the local galaxy population. The shape and scatter of both the star-formation main sequence and the mass-metallicity relation are deeply linked to the availability of atomic and molecular gas. Future progress will come from expanding our exploration of scaling relations into new parameter space (in particular, the regime of dwarf galaxies), better connecting the cold ISM of large samples of galaxies with the environment that feeds them (the circumgalactic medium, in particular), and understanding the impact of these large scales on the efficiency of the star-formation process on molecular cloud scales.

August 2022: Saintonge, A; Catinella, B (Annual Review of Astronomy and Astrophysics)

The Transmission Spectrum of WASP-17 b From the Optical to the Near-infrared Wavelengths: Combining STIS, WFC3, and IRAC Data Sets

We present the transmission spectrum of the inflated hot Jupiter WASP-17 b, observed with the STIS and WFC3 instruments aboard the Hubble Space Telescope, allowing for a continuous wavelength coverage from ~0.4 to ~1.7 μm. Observations taken with IRAC channels 1 and 2 on the Spitzer Space Telescope are also included, adding photometric measurements at 3.6 and 4.5 μm. HST spectral data were analyzed with Iraclis, a pipeline specialized in the reduction of STIS and WFC3 transit and eclipse observations. Spitzer photometric observations were reduced with the TLCD-LSTM method, utilizing recurrent neural networks. The outcome of our reduction produces incompatible results between STIS visit 1 and visit 2, which leads us to consider two scenarios for G430L. Additionally, by modeling the WFC3 data alone, we can extract atmospheric information without having to deal with the contrasting STIS data sets. We run separate retrievals on the three spectral scenarios with the aid of TauREx 3, a fully Bayesian retrieval framework. We find that, independently of the data considered, the exoplanet atmosphere displays strong water signatures and, potentially, the presence of aluminum oxide and titanium hydride. A retrieval that includes an extreme photospheric activity of the host star is the preferred model, but we recognize that such a scenario is unlikely for an F6-type star. Due to the incompleteness of all STIS spectral light curves, only further observations with this instrument would allow us to properly constrain the atmospheric limb of WASP-17 b, before the James Webb Space Telescope or Ariel will come online.

July 2022: Saba, A; Tsiaras, A; Morvan, M; Thompson, A; Changeat, Q; et al. (The Astronomical Journal)

The Effects of Cosmic Rays on the Chemistry of Dense Cores

Cosmic rays are crucial to the chemistry of molecular clouds and their evolution. They provide essential ionizations, dissociations, heating, and energy to the cold, dense cores. As cosmic rays pierce through clouds they are attenuated and lose energy, which leads to a dependency on the column density of a system. The detailed effects these particles have on the central regions still need to be fully understood. Here, we revisit how cosmic rays are treated in the UCLCHEM chemical modeling code by including both ionization rate and H₂ dissociation rate dependencies alongside the production of cosmic ray induced excited species and we study in detail the effects of these treatments on the chemistry of pre-stellar cores. We find that these treatments can have significant effects on chemical abundances, up to several orders of magnitude, depending on the physical conditions. The ionization dependency is the most significant treatment influencing chemical abundances through the increased presence of ionized species, grain desorptions, and enhanced chemical reactions. Comparisons to chemical abundances derived from observations show the new treatments reproduce these observations better than the standard handling. It is clear that more advanced treatments of cosmic rays are essential to chemical models and that including this type of dependency provides more accurate chemical representations.

July 2022: O'Donoghue, R; Viti, S; Padovani, M; James, T (The Astrophysical Journal)

Stellar populations and star formation histories of the most extreme [O III] emitters at z = 1.3 - 3.7

As the James Webb Space Telescope approaches scientific operation, there is much interest in exploring the redshift range beyond that accessible with Hubble Space Telescope imaging. Currently, the only means to gauge the presence of such early galaxies is to age-date the stellar population of systems in the reionisation era. As a significant fraction of z ≃ 7-8 galaxies are inferred from Spitzer photometry to have extremely intense [O III] emission lines, it is commonly believed these are genuinely young systems that formed at redshifts z < 10, consistent with a claimed rapid rise in the star formation density at that time. Here, we study a spectroscopically confirmed sample of extreme [O III] emitters at z = 1.3-3.7, using both dynamical masses estimated from [O III] line widths and rest-frame UV to near-infrared photometry to illustrate the dangers of assuming such systems are genuinely young. For the most extreme of our intermediate redshift line emitters, we find dynamical masses 10-100 times that associated with a young stellar population mass, which are difficult to explain solely by the presence of additional dark matter or gaseous reservoirs. Adopting non-parametric star formation histories, we show how the near-infrared photometry of a subset of our sample reveals an underlying old (>100 Myr) population whose stellar mass is ≃ 40 times that associated with the starburst responsible for the extreme line emission. Without adequate rest-frame near-infrared photometry, we argue it may be premature to conclude that extreme line emitters in the reionisation era are low-mass systems that formed at redshifts below z ≃ 10.

July 2022: Tang, M; Stark, D; Ellis, R (Monthly Notices of the Royal Astronomical Society)

Cosmology and neutrino mass with the minimum spanning tree

The information content of the minimum spanning tree (MST), used to capture higher order statistics and information from the cosmic web, is compared to that of the power spectrum for a νΛCDM model. The measurements are made in redshift space using haloes from the Quijote simulation of mass $\ge 3.2\times 10^{13}\, h^{-1}\, {\rm M}_{\odot }$ in a box of length $L_{\rm box}=1\, h^{-1}\, {\rm Gpc}$. The power spectrum multipoles (monopole and quadrupole) are computed for Fourier modes in the range $0.006\, h{\rm Mpc}^{-1} \lt k \lt 0.5\, h{\rm Mpc}^{-1}$. For comparison the MST is measured with a minimum length-scale of $l_{\min }\simeq 13\, h^{-1}\, {\rm Mpc}$. Combining the MST and power spectrum allows for many of the individual degeneracies to be broken; on its own the MST provides tighter constraints on the sum of neutrino masses M_ν and cosmological parameters h, n_s, and Ω_b but the power spectrum alone provides tighter constraints on Ω_m and σ₈. Combined we find constraints that are a factor of two (or greater) on all parameters with respect to the power spectrum (for M_ν there is a factor of four improvement). These improvements appear to be driven by the MST's sensitivity to small scale clustering, where the effect of neutrino free-streaming becomes relevant, and high-order statistical information in the cosmic web. The MST is shown to be a powerful tool for cosmology and neutrino mass studies, and therefore could play a pivotal role in ongoing and future galaxy redshift surveys (such as DES, DESI, Euclid, and Rubin-LSST).

July 2022: Naidoo, K; Massara, E; Lahav, O (Monthly Notices of the Royal Astronomical Society)

The Ariel Target List: The Impact of TESS and the Potential for Characterizing Multiple Planets within a System

The ESA Ariel mission has been adopted for launch in 2029 and will conduct a survey of around 1000 exoplanetary atmospheres during its primary mission life. By providing homogeneous data sets with a high signal-to-noise ratio and wide wavelength coverage, Ariel will unveil the atmospheric demographics of these faraway worlds, helping to constrain planet formation and evolution processes on a galactic scale. Ariel seeks to undertake a statistical survey of a diverse population of planets; therefore, the sample of planets from which this selection can be made is of the utmost importance. While many suitable targets have already been found, hundreds more will be discovered before the mission is operational. Previous studies have used predictions of exoplanet detections to forecast the available planet population by the launch date of Ariel, with the most recent noting that the Transiting Exoplanet Survey Satellite (TESS) alone should provide over 1000 potential targets. In this work, we consider the planet candidates found to date by TESS to show that, with the addition of already confirmed planets, Ariel will already have a more than sufficient sample to choose its target list from once these candidates are validated. We showcase the breadth of this population, as well as exploring, for the first time, the ability of Ariel to characterize multiple planets within a single system. Comparative planetology of worlds orbiting the same star, as well as across the wider population, will undoubtedly revolutionize our understanding of planet formation and evolution.

July 2022: Edwards, B; Tinetti, G (The Astronomical Journal)

Cross-sections for heavy atmospheres: H₂O self-broadening

The discovery of super-Earth and mini-Neptune exoplanets means that atmospheric signals from low-mass, temperate exoplanets are being increasingly studied. The signal acquired as the planet transits its host star, known as the transit depth, is smaller for these planets and, as such, more difficult to analyze. The launch of the space telescopes James Webb (JWST) & Ariel will give rise to an explosion in the quality and quantity of spectroscopic data available for an unprecedented number of exoplanets in our galaxy. Accurately extracting the information content, thereby permitting atmospheric science, of such data-sets will require robust models and techniques. We present here the analysis of simulated transmission spectra for water-rich atmospheres, giving evidence for non-negligible differences in simulated transit depths when self-broadening of H₂O is correctly accounted for, compared with the currently typically accepted standard of using H₂ and He-broadened cross-sections. Our case-study analysis is carried out on two super-Earths, focusing on water-based atmospheres, ranging from H₂-rich to H₂O-rich. The transit depth is considerably affected, increasing values by up to 60 ppm, which is shown to be detectable with JWST and Ariel. The differences are most pronounced for the lighter (i.e. μ ∼ 4) atmospheres. Our work illustrates that it is imperative that the field of exoplanet spectroscopy moves toward adapted cross-sections, increasingly optimized for high- μ atmospheres for studies of super-Earths and mini-Neptunes.

June 2022: Anisman, L; Chubb, K; Changeat, Q; Edwards, B; Yurchenko, S; et al. (Journal of Quantitative Spectroscopy and Radiative Transfer)

Energizing Star Formation: The Cosmic-Ray Ionization Rate in NGC 253 Derived from ALCHEMI Measurements of H₃O⁺ and SO

The cosmic-ray ionization rate (CRIR) is a key parameter in understanding the physical and chemical processes in the interstellar medium. Cosmic rays are a significant source of energy in star formation regions, impacting the physical and chemical processes that drive the formation of stars. Previous studies of the circum-molecular zone of the starburst galaxy NGC 253 have found evidence for a high CRIR value: 10³-10⁶ times the average CRIR within the Milky Way. This is a broad constraint, and one goal of this study is to determine this value with much higher precision. We exploit ALMA observations toward the central molecular zone of NGC 253 to measure the CRIR. We first demonstrate that the abundance ratio of H₃O⁺ and SO is strongly sensitive to the CRIR. We then combine chemical and radiative transfer models with nested sampling to infer the gas properties and CRIR of several star-forming regions in NGC 253 from emission from their transitions. We find that each of the four regions modeled has a CRIR in the range (1-80) × 10^-14 s^-1 and that this result adequately fits the abundances of other species that are believed to be sensitive to cosmic rays, including C₂H, HCO⁺, HOC⁺, and CO. From shock and photon-dominated/X-ray dominated region models, we further find that neither UV-/X-ray-driven nor shock-dominated chemistry is a viable single alternative as none of these processes can adequately fit the abundances of all of these species.

June 2022: Holdship, J; Mangum, J; Viti, S; Behrens, E; Harada, N; et al. (The Astrophysical Journal)

Forecasting the potential of weak lensing magnification to enhance LSST large-scale structure analyses

Recent works have shown that weak lensing magnification must be included in upcoming large-scale structure analyses, such as for the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), to avoid biasing the cosmological results. In this work, we investigate whether including magnification has a positive impact on the precision of the cosmological constraints, as well as being necessary to avoid bias. We forecast this using an LSST mock catalogue and a halo model to calculate the galaxy power spectra. We find that including magnification has little effect on the precision of the cosmological parameter constraints for an LSST galaxy clustering analysis, where the halo model parameters are additionally constrained by the galaxy luminosity function. In particular, we find that for the LSST gold sample (i < 25.3) including weak lensing magnification only improves the galaxy clustering constraint on Ω_m by a factor of 1.03, and when using a very deep LSST mock sample (i < 26.5) by a factor of 1.3. Since magnification predominantly contributes to the clustering measurement and provides similar information to that of cosmic shear, this improvement would be reduced for a combined galaxy clustering and shear analysis. We also confirm that not modelling weak lensing magnification will catastrophically bias the cosmological results from LSST. Magnification must therefore be included in LSST large-scale structure analyses even though it does not significantly enhance the precision of the cosmological constraints.

June 2022: Mahony, C; Fortuna, M; Joachimi, B; Korn, A; Hoekstra, H; et al. (Monthly Notices of the Royal Astronomical Society)

Non-local thermal equilibrium spectra of atmospheric molecules for exoplanets

Here we present a study of non-local thermodynamic equilibrium (LTE) effects on the exoplanetary spectra of a collection of molecules that are key in the investigation of exoplanet atmospheres: water, methane, carbon monoxide, and titanium oxide. These molecules are chosen as examples of different spectral ranges (infrared and ultraviolet), molecular types (diatomics and polyatomics), and spectral types (electronic and rovibrational); the importance of different vibrational bands in forming distinct non-LTE spectral features is investigated. Most notably, such key spectral signatures for distinguishing between the LTE and non-LTE cases include: for CH₄ the 3.15 $\mu$m band region; for H₂O the 2.0 and 2.7 $\mu$m band regions; for TiO, a strong variation in intensity in the bands between 0.5 and 0.75 $\mu$m; and a sole CO signature between 5 and 6 $\mu$m. […]

May 2022: Wright, Sam O. M., Waldmann, Ingo, Yurchenko, Sergei N. (Monthly Notices of the Royal Astronomical Society)

Deep learning methods for obtaining photometric redshift estimations from images

Knowing the redshift of galaxies is one of the first requirements of many cosmological experiments, and as it is impossible to perform spectroscopy for every galaxy being observed, photometric redshift (photo-z) estimations are still of particular interest. Here, we investigate different deep learning methods for obtaining photo-z estimates directly from images, comparing these with 'traditional' machine learning algorithms which make use of magnitudes retrieved through photometry. As well as testing a convolutional neural network (CNN) and inception-module CNN, we introduce a novel mixed-input model that allows for both images and magnitude data to be used in the same model as a way of further improving the estimated redshifts. […]

May 2022: Henghes, Ben, Thiyagalingam, Jeyan, Pettitt, Connor, Hey, Tony, Lahav, Ofer (Monthly Notices of the Royal Astronomical Society)

COSMOPOWER: emulating cosmological power spectra for accelerated Bayesian inference from next-generation surveys

We present COSMOPOWER, a suite of neural cosmological power spectrum emulators providing orders-of-magnitude acceleration for parameter estimation from two-point statistics analyses of Large-Scale Structure (LSS) and Cosmic Microwave Background (CMB) surveys. The emulators replace the computation of matter and CMB power spectra from Boltzmann codes; thus, they do not need to be re-trained for different choices of astrophysical nuisance parameters or redshift distributions. The matter power spectrum emulation error is less than $0.4{{\ \rm per\ cent}}$ in the wavenumber range $k \in [10^{-5}, 10] \, \mathrm{Mpc}^{-1}$ for redshift z ∈ [0, 5]. […]

April 2022: Spurio Mancini, Alessio, Piras, Davide, Alsing, Justin, Joachimi, Benjamin, Hobson, Michael P. (Monthly Notices of the Royal Astronomical Society)

ExoMol line lists - XLV. Rovibronic molecular line lists of calcium monohydride (CaH) and magnesium monohydride (MgH)

New molecular line lists for calcium monohydride (⁴⁰Ca¹H) and magnesium monohydride (²⁴Mg¹H) and its minor isotopologues (²⁵Mg¹H and ²⁶Mg¹H) are presented. The rotation-vibration-electronic (rovibronic) line lists, named XAB, consider transitions involving the $X\, {}^{2}\Sigma ^{+}$, $A\, {}^{2}\Pi$, and $B/B^{\prime }\, {}^{2}\Sigma ^{+}$ electronic states in the 0-30 000 cm^-1 region (wavelengths λ > 0.33 μm) and are suitable for temperatures up to 5000 K. A comprehensive analysis of the published spectroscopic literature on CaH and MgH is used to obtain new extensive data sets of accurate rovibronic energy levels with measurement uncertainties and consistent quantum number labelling. […]

April 2022: Owens, Alec, Dooley, Sophie, McLaughlin, Luke, Tan, Brandon, Zhang, Guanming, et al (Monthly Notices of the Royal Astronomical Society)

ExoMol molecular line lists - XLIII. Rovibronic transitions corresponding to the close-lying X ²Π and A ²Σ⁺ states of NaO

The sodium monoxide radical (NaO) is observed in night-glow in the Earth's mesosphere and likely has astronomical importance. This study concerns the optical transitions within the ground X ²Π state and to the very low-lying (T_e ≍ 2000 cm^-1) excited A ²Σ⁺ state. A line list consisting of rovibronic term values, allowed electric dipole transitions, Einstein coefficients, and partition functions for varying temperature are produced using a variational solution of the coupled-channel Schrödinger equations using the program DUO. […]

April 2022: Mitev, G. B., Taylor, S., Tennyson, Jonathan, Yurchenko, S. N., Buchachenko, A. A., et al (Monthly Notices of the Royal Astronomical Society)

Explaining deep learning of galaxy morphology with saliency mapping

We successfully demonstrate the use of explainable artificial intelligence (XAI) techniques on astronomical data sets in the context of measuring galactic bar lengths. The method consists of training convolutional neural networks on human classified data from Galaxy Zoo in order to predict general galaxy morphologies, and then using SMOOTHGRAD (a saliency mapping technique) to extract the bar for measurement by a bespoke algorithm. We contrast this to another method of using a convolutional neural network to directly predict galaxy bar lengths. […]

April 2022: Bhambra, Prabh, Joachimi, Benjamin, Lahav, Ofer (Monthly Notices of the Royal Astronomical Society)

Relentless and complex transits from a planetesimal debris disc

This article reports quasi-continuous transiting events towards WD 1054-226 at d = 36.2 pc and V = 16.0 mag, based on simultaneous, high-cadence, multiwavelength imaging photometry using ULTRACAM over 18 nights from 2019 to 2020 March. The predominant period is 25.02 h and corresponds to a circular orbit with blackbody T_eq = 323 K, where a planetary surface can nominally support liquid water. The light curves reveal remarkable night-to-night similarity, with changes on longer time-scales, and lack any transit-free segments of unocculted starlight. […]

April 2022: Farihi, J., Hermes, J. J., Marsh, T. R., Mustill, A. J., Wyatt, M. C., et al (Monthly Notices of the Royal Astronomical Society)

Infrared scaling for a graviton condensate

The coupling between gravity and matter provides an intriguing length scale in the infrared for theories of gravity within Einstein-Hilbert action and beyond. In particular, we will show that such an infrared length scale is determined by the number of gravitons N_g ≫ 1 associated to a given mass in the non-relativistic limit. After tracing out the matter degrees of freedom, the graviton vacuum is found to be in a displaced vacuum with an occupation number of gravitons N_g ≫ 1. […]

April 2022: Bose, Sougato, Mazumdar, Anupam, Toroš, Marko (Nuclear Physics B)

On-sky validation of image-based adaptive optics wavefront sensor referencing

Context. Differentiating between a true exoplanet signal and residual speckle noise is a key challenge in high-contrast imaging (HCI). Speckles result from a combination of fast, slow, and static wavefront aberrations introduced by atmospheric turbulence and instrument optics. […]

March 2022: Skaf, Nour, Guyon, Olivier, Gendron, Éric, Ahn, Kyohoon, Bertrou-Cantou, Arielle, et al (Astronomy and Astrophysics)

3D Line Radiative Transfer & Synthetic Observations with Magritte

March 2022: De Ceuster, Frederik, Ceulemans, Thomas, Srivastava, Atulit, Homan, Ward, Bolte, Jan, et al (The Journal of Open Source Software)

On Spectroscopic Phase-curve Retrievals: H₂ Dissociation and Thermal Inversion in the Atmosphere of the Ultrahot Jupiter WASP-103 b

This work presents a reanalysis of the spectroscopic phase-curve observations of the ultrahot Jupiter WASP-103 b obtained by the Hubble Space Telescope (HST) and the Spitzer Telescope. Traditional 1D and unified 1.5D spectral retrieval techniques are employed, allowing to map the thermal structure and the abundances of trace gases in this planet as a function of longitude. On the dayside, the atmosphere is found to have a strong thermal inversion, with indications of thermal dissociation traced by continuum H^- opacity. […]

March 2022: Changeat, Quentin (The Astronomical Journal)

GOLDRUSH. IV. Luminosity Functions and Clustering Revealed with 4,000,000 Galaxies at z 2-7: Galaxy-AGN Transition, Star Formation Efficiency, and Implication for Evolution at z > 10

We present new measurements of rest-UV luminosity functions and angular correlation functions from 4,100,221 galaxies at z ~ 2-7 identified in the Subaru/Hyper Suprime-Cam survey and CFHT Large Area U-band Survey. The obtained luminosity functions at z ~ 4-7 cover a very wide UV luminosity range of ~ $0.002\mbox{--}2000{L}_{\mathrm{UV}}^{* }$ combined with previous studies, confirming that the dropout luminosity function is a superposition of the active galactic nucleus (AGN) luminosity function dominant at M _UV ≲ -24 mag and the galaxy luminosity function dominant at M _UV ≳ -22 mag, consistent with galaxy fractions based on 1037 spectroscopically identified sources. Galaxy luminosity functions estimated from the spectroscopic galaxy fractions show the bright-end excess beyond the Schechter function at ≳2σ levels, possibly made by inefficient mass quenching, low dust obscuration, and/or hidden AGN activity. […]

March 2022: Harikane, Yuichi, Ono, Yoshiaki, Ouchi, Masami, Liu, Chengze, Sawicki, Marcin, et al (The Astrophysical Journal Supplement Series)

No strong dependence of Lyman continuum leakage on physical properties of star-forming galaxies at ≲ z ≲ 3.5

We present Lyman continuum (LyC) radiation escape fraction (f_esc) measurements for 183 spectroscopically confirmed star-forming galaxies in the redshift range 3.11 < z < 3.53 in the Chandra Deep Field South. We use ground-based imaging to measure f_esc, and use ground- and space-based photometry to derive galaxy physical properties using spectral energy distribution (SED) fitting. We additionally derive [O III] + H β equivalent widths (that fall in the observed K band) by including nebular emission in SED fitting. […]

March 2022: Saxena, A., Pentericci, L., Ellis, R. S., Guaita, L., Calabrò, A., et al (Monthly Notices of the Royal Astronomical Society)

Forecasting the potential of weak lensing magnification to enhance LSST large-scale structure analyses

March 2022: Mahony, Constance, Fortuna, Maria Cristina, Joachimi, Benjamin, Korn, Andreas, Hoekstra, Henk, et al (Monthly Notices of the Royal Astronomical Society)

Single frequency CMB B-mode inference with realistic foregrounds from a single training image

With a single training image and using wavelet phase harmonic augmentation, we present polarized Cosmic Microwave Background (CMB) foreground marginalization in a high-dimensional likelihood-free (Bayesian) framework. We demonstrate robust foreground removal using only a single frequency of simulated data for a BICEP-like sky patch. Using Moment Networks, we estimate the pixel-level posterior probability for the underlying {E, B} signal and validate the statistical model with a quantile-type test using the estimated marginal posterior moments. […]

February 2022: Jeffrey, Niall, Boulanger, François, Wandelt, Benjamin D., Regaldo-Saint Blancard, Bruno, Allys, Erwan, et al (Monthly Notices of the Royal Astronomical Society)

Considerations for Optimizing the Photometric Classification of Supernovae from the Rubin Observatory

The Vera C. Rubin Observatory will increase the number of observed supernovae (SNe) by an order of magnitude; however, it is impossible to spectroscopically confirm the class for all SNe discovered. Thus, photometric classification is crucial, but its accuracy depends on the not-yet-finalized observing strategy of Rubin Observatory's Legacy Survey of Space and Time (LSST). […]

February 2022: Alves, Catarina S., Peiris, Hiranya V., Lochner, Michelle, McEwen, Jason D., Allam, Tarek, et al (The Astrophysical Journal Supplement Series)

Measuring Chemical Likeness of Stars with Relevant Scaled Component Analysis

Identification of chemically similar stars using elemental abundances is core to many pursuits within Galactic archeology. However, measuring the chemical likeness of stars using abundances directly is limited by systematic imprints of imperfect synthetic spectra in abundance derivation. We present a novel data-driven model that is capable of identifying chemically similar stars from spectra alone. […]

February 2022: de Mijolla, Damien, Ness, Melissa K. (The Astrophysical Journal)

History-independent tracers. Forgetful molecular probes of the physical conditions of the dense interstellar medium

Context. Molecular line emission is a powerful probe of the physical conditions of astrophysical objects but can be complex to model, and it is often unclear which transitions would be the best targets for observers who wish to constrain a given parameter.
Aims: We produce a list of molecular species for which the gas history can be ignored, removing a major modelling complexity. […]

February 2022: Holdship, J., Viti, S. (Astronomy and Astrophysics)

ExoMol line lists - XLIV. Infrared and ultraviolet line list for silicon monoxide (²⁸Si¹⁶O)

A new silicon monoxide (²⁸Si¹⁶O) line list covering infrared, visible, and ultraviolet regions called SiOUVenIR is presented. This line list extends the infrared EBJT ExoMol line list by including vibronic transitions to the $A\, {}^{1}\Pi$ and $E\, {}^{1}\Sigma ^{+}$ electronic states. Strong perturbations to the $A\, {}^{1}\Pi$ band system are accurately modelled through the treatment of six dark electronic states: $C\, {}^{1}\Sigma ^{-}$, $D\, {}^{1}\Delta$, $a\, {}^{3}\Sigma ^{+}$, $b\, {}^{3}\Pi$, $e\, {}^{3}\Sigma ^{-}$, and $d\, {}^{3}\Delta$. […]

February 2022: Yurchenko, Sergei N., Tennyson, Jonathan, Syme, Anna-Maree, Adam, Ahmad Y., Clark, Victoria H. J., et al (Monthly Notices of the Royal Astronomical Society)

Cross-sections for heavy atmospheres: H₂O continuum

Most of the exoplanets detected up to now transit in front of their host stars, allowing for the generation of transmission spectra; the study of exoplanet atmospheres relies heavily upon accurate analysis of these spectra. Recent discoveries mean that the study of atmospheric signals from low-mass, temperate worlds are becoming increasingly common. The observed transit depth in these planets is small and more difficult to analyze. […]

February 2022: Anisman, Lara O., Chubb, Katy L., Elsey, Jonathan, Al-Refaie, Ahmed, Changeat, Quentin, et al (Journal of Quantitative Spectroscopy and Radiative Transfer)

Sewing spacetime with Lorentzian threads: complexity and the emergence of time in quantum gravity

Holographic entanglement entropy was recently recast in terms of Riemannian flows or `bit threads'. We consider the Lorentzian analog to reformulate the `complexity=volume' conjecture using Lorentzian flows — timelike vector fields whose minimum flux through a boundary subregion is equal to the volume of the homologous maximal bulk Cauchy slice. By the nesting of Lorentzian flows, holographic complexity is shown to obey a number of properties. […]

February 2022: Pedraza, Juan F., Russo, Andrea, Svesko, Andrew, Weller-Davies, Zachary (Journal of High Energy Physics)

White dwarfs identified in LAMOST Data Release 5

In this paper, we report white dwarfs (WD) identified in the 5^th Data Release of the Large Area Multi-Object fibre Spectroscopic Telescope (LAMOST), including spectral types of DA, DB, DC, DZ, and so on. There are 2625 DA spectra of 2281 DA stars, 182 DB spectra of 166 DB stars, 62 DC spectra of 58 DC stars, 36 DZ spectra of 33 DZ stars, and many other types identified, in addition to our previous paper (Data Release 2). Amongst those sources, 393 DA stars and 46 DB stars are new identifications after cross-matching with the literature. […]

January 2022: Guo, Jincheng, Zhao, Jingkun, Zhang, Huawei, Zhang, Jiajun, Bai, Yu, et al (Monthly Notices of the Royal Astronomical Society)

Biosignatures Associated with Organic Matter in Late Paleoproterozoic Stromatolitic Dolomite and Implications for Martian Carbonates

The documentation of biosignatures in Precambrian rocks is an important requirement in the search for evidence of life on other ancient planetary surfaces. Three major kinds of biosignatures are crucially important: primary microbial sedimentary textures, diagenetic organomineral assemblages, and stable isotope compositions. This study presents new petrographic, mineralogical, and organic geochemical analyses of biosignatures in dolomitic stromatolites from the Pethei Group (N.W.T., Canada) and the Kasegalik Formation of the Belcher Group (Nunavut, Canada). […]

January 2022: Goodwin, Arthur, Papineau, Dominic (Astrobiology)

Supernova induced processing of interstellar dust: impact of interstellar medium gas density and gas turbulence

Quantifying the efficiency of dust destruction in the interstellar medium (ISM) due to supernovae (SNe) is crucial for the understanding of galactic dust evolution. We present 3D hydrodynamic simulations of an SN blast wave propagating through the ISM. The interaction between the forward shock of the remnant and the surrounding ISM leads to destruction of ISM dust by the shock-heated gas. […]

January 2022: Kirchschlager, Florian, Mattsson, Lars, Gent, Frederick A. (Monthly Notices of the Royal Astronomical Society)

Spectroscopy of an extreme [O III] emitting active galactic nucleus at z = 3.212: implications for the reionization era

Reionization-era galaxies often display intense nebular emission lines, both in rest-frame optical ([O III] + H β) and ultraviolet (UV; C III], C IV). How such strong nebular emission is powered remains unclear, with both active galactic nuclei (AGNs) and hot stars considered equally viable. The UV continuum slopes of these early systems tend to be very blue (β < -2), reflecting minimal dust obscuration, young ages, and low metallicities. […]

January 2022: Tang, Mengtao, Stark, Daniel P., Ellis, Richard S., Charlot, Stéphane, Feltre, Anna, et al (Monthly Notices of the Royal Astronomical Society)

Observational Limits on the Early-time Dust Mass in SN 1987A

In recent years, dust masses of a few tenths of a solar mass have been found in the expanding ejecta of a number of core-collapse supernovae. How dust forms in such quantities remains poorly understood; theories of dust formation predict lower total masses and much faster formation rates than observations imply. One suggestion to reconcile observations and theory was made by Dwek et al., who proposed that the dust forms very rapidly, and because of its optical depth, is not initially observationally detectable, only being gradually revealed as the ejecta expand. […]

December 2021: Wesson, Roger, Bevan, Antonia (The Astrophysical Journal)

A high-resolution line list for AlO

Indications of aluminium monoxide in atmospheres of exoplanets are being reported. Studies using high-resolution spectroscopy should allow a strong detection but require high-accuracy laboratory data. A MARVEL (measured active rotational-vibrational energy levels) analysis is performed for the available spectroscopic data on ²⁷Al¹⁶O: 22 473 validated transitions are used to determine 6485 distinct energy levels. […]

December 2021: Bowesman, Charles A., Shuai, Meiyin, Yurchenko, Sergei N., Tennyson, Jonathan (Monthly Notices of the Royal Astronomical Society)

Semi-classical thermodynamics of quantum extremal surfaces in Jackiw-Teitelboim gravity

Quantum extremal surfaces (QES), codimension-2 spacelike regions which extremize the generalized entropy of a gravity-matter system, play a key role in the study of the black hole information problem. The thermodynamics of QESs, however, has been largely unexplored, as a proper interpretation requires a detailed understanding of backreaction due to quantum fields. We investigate this problem in semi-classical Jackiw-Teitelboim (JT) gravity, where the spacetime is the eternal two-dimensional Anti-de Sitter (AdS₂) black hole, Hawking radiation is described by a conformal field theory with central charge c, and backreaction effects may be analyzed exactly. […]

December 2021: Pedraza, Juan F., Svesko, Andrew, Sybesma, Watse, Visser, Manus R. (Journal of High Energy Physics)

Proper motions of OB stars in the far Carina Arm

In large-scale maps of the Galactic disc, the Carina Arm stands out as a clear spiral feature, hosting prominent star clusters and associations rich in massive stars. We study the proper motions of 4199 O and early B most likely in the far Carina Arm, at distances mainly in excess of 4 kpc from the Sun, within the sky region, 282° < ℓ < 294° and -3° < b < +1° (Galactic coordinates). The sample is constructed by extending an existing blue-selected catalogue, and cross-matching with Gaia EDR3 astrometry. […]

December 2021: Drew, J. E., Monguió, M., Wright, N. J. (Monthly Notices of the Royal Astronomical Society)

The vibrational properties of benzene on an ordered water ice surface

We present a hybrid CCSD(T) + PBE-D3 approach to calculating the vibrational signatures for gas-phase benzene and benzene adsorbed on an ordered water ice surface. We compare the results of our method against experimentally recorded spectra and calculations performed using PBE-D3-only approaches (harmonic and anharmonic). Calculations use a proton ordered XIh water ice surface consisting of 288 water molecules, and results are compared against experimental spectra recorded for an ASW ice surface. […]

December 2021: Clark, Victoria H. J., Benoit, David M. (Monthly Notices of the Royal Astronomical Society)

Outflows from starburst galaxies with various driving mechanisms and their X-ray properties

Outflows in starburst galaxies driven by thermal-mechanical energy, cosmic rays, and their mix are investigated with 1D and 2D hydrodynamic simulations. We show that these outflows could reach a stationary state, after which their hydrodynamic profiles asymptotically approach previous results obtained semi-analytically for stationary outflow configurations. The X-rays from the simulated outflows are computed, and high-resolution synthetic spectra and broad-band light curves are constructed. […]

December 2021: Yu, B. P. Brian, Owen, Ellis R., Pan, Kuo-Chuan, Wu, Kinwah, Ferreras, Ignacio (Monthly Notices of the Royal Astronomical Society)

Lorentzian Threads as Gatelines and Holographic Complexity

The continuous min flow-max cut principle is used to reformulate the "complexity=volume " conjecture using Lorentzian flows—divergenceless norm-bounded timelike vector fields whose minimum flux through a boundary subregion is equal to the volume of the homologous maximal bulk Cauchy slice. The nesting property is used to show the rate of complexity is bounded below by "conditional complexity," describing a multistep optimization with intermediate and final target states. Conceptually, discretized Lorentzian flows are interpreted in terms of threads or gatelines such that complexity is equal to the minimum number of gatelines used to prepare a conformal field theory (CFT) state by an optimal tensor network (TN) discretizing the state. […]

December 2021: Pedraza, Juan F., Russo, Andrea, Svesko, Andrew, Weller-Davies, Zachary (Physical Review Letters)

A buyer's guide to the Hubble constant

Since the expansion of the universe was first established by Edwin Hubble and Georges Lemaître about a century ago, the Hubble constant H₀ which measures its rate has been of great interest to astronomers. Besides being interesting in its own right, few properties of the universe can be deduced without it. In the last decade, a significant gap has emerged between different methods of measuring it, some anchored in the nearby universe, others at cosmological distances. […]

December 2021: Shah, Paul, Lemos, Pablo, Lahav, Ofer (Astronomy and Astrophysics Review)

The causal effect of environment on halo mass and concentration

Understanding the impact of environment on the formation and evolution of dark matter haloes and galaxies is a crucial open problem. Studying statistical correlations in large simulated populations sheds some light on these impacts, but the causal effect of an environment on individual objects is harder to pinpoint. Addressing this, we present a new method for resimulating a single dark matter halo in multiple large-scale environments. […]

November 2021: Cadiou, Corentin, Pontzen, Andrew, Peiris, Hiranya V., Lucie-Smith, Luisa (Monthly Notices of the Royal Astronomical Society)

Geometry versus growth. Internal consistency of the flat ΛCDM model with KiDS-1000

We carry out a multi-probe self-consistency test of the flat Lambda Cold Dark Matter (ΛCDM) model with the aim of exploring potential causes of the reported tensions between high- and low-redshift cosmological observations. We divide the model into two theory regimes determined by the smooth background (geometry) and the evolution of matter density fluctuations (growth), each governed by an independent set of ΛCDM cosmological parameters. This extended model is constrained by a combination of weak gravitational lensing measurements from the Kilo-Degree Survey, galaxy clustering signatures extracted from Sloan Digital Sky Survey campaigns and the Six-Degree Field Galaxy Survey, and the angular baryon acoustic scale and the primordial scalar fluctuation power spectrum measured in Planck cosmic microwave background (CMB) data. […]

November 2021: Ruiz-Zapatero, Jaime, Stölzner, Benjamin, Joachimi, Benjamin, Asgari, Marika, Bilicki, Maciej, et al (Astronomy and Astrophysics)

Peeking inside the Black Box: Interpreting Deep-learning Models for Exoplanet Atmospheric Retrievals

Deep-learning algorithms are growing in popularity in the field of exoplanetary science due to their ability to model highly nonlinear relations and solve interesting problems in a data-driven manner. Several works have attempted to perform fast retrievals of atmospheric parameters with the use of machine-learning algorithms like deep neural networks (DNNs). Yet, despite their high predictive power, DNNs are also infamous for being "black boxes." It is their apparent lack of explainability that makes the astrophysics community reluctant to adopt them. […]

November 2021: Yip, Kai Hou, Changeat, Quentin, Nikolaou, Nikolaos, Morvan, Mario, Edwards, Billy, et al (The Astronomical Journal)

Quantifying the rarity of the local super-volume

We investigate the extent to which the number of clusters of mass exceeding $10^{15}\, M_{\odot }\, h^{-1}$ within the local super-volume ($\lt 135\mathrm{\, Mpc\, }h^{-1}$) is compatible with the standard ΛCDM cosmological model. Depending on the mass estimator used, we find that the observed number N of such massive structures can vary between 0 and 5. Adopting N = 5 yields ΛCDM likelihoods as low as 2.4 × 10^-3 (with σ₈ = 0.81) or 3.8 × 10^-5 (with σ₈ = 0.74). […]

November 2021: Stopyra, Stephen, Peiris, Hiranya V., Pontzen, Andrew, Jasche, Jens, Natarajan, Priyamvada (Monthly Notices of the Royal Astronomical Society)

Qudits for witnessing quantum-gravity-induced entanglement of masses under decoherence

Recently, a theoretical and an experimental protocol known as quantum-gravity-induced entanglement of masses (QGEM) has been proposed to test the quantum nature of gravity using two mesoscopic masses, each placed in a superposition of two locations. If after eliminating all nongravitational interactions between them the particles become entangled, one can conclude that the gravitational potential is induced via a quantum mediator, i.e., graviton. In this paper we explore extensions of the QGEM experiment to multidimensional quantum objects and examine a range of different experiment geometries, in order to determine which would generate entanglement faster. […]

November 2021: Tilly, Jules, Marshman, Ryan J., Mazumdar, Anupam, Bose, Sougato (Physical Review A)

Large-scale clustering amongst Fermi blazars; evidence for axis alignments?

We find evidence for large-scale clustering amongst Fermi-selected BL Lac objects but not amongst Fermi-selected flat spectrum radio quasars (FSRQs). Using two-point correlation functions, we have investigated the clustering properties of different classes of objects from the Fermi-LAT(Large Area Telescope) 4FGL catalogue. We wanted to test the idea based on optical polarization observations that there might be large volumes of space in which AGN axes are aligned. […]

October 2021: Marchã, M. J. M., Browne, I. W. A. (Monthly Notices of the Royal Astronomical Society)

The distribution and origin of C₂H in NGC 253 from ALCHEMI

Context. Observations of chemical species can provide insights into the physical conditions of the emitting gas however it is important to understand how their abundances and excitation vary within different heating environments. C₂H is a molecule typically found in PDR regions of our own Galaxy but there is evidence to suggest it also traces other regions undergoing energetic processing in extragalactic environments. […]

October 2021: Holdship, J., Viti, S., Martín, S., Harada, N., Mangum, J., et al (Astronomy and Astrophysics)

Carbon-enhanced stars with short orbital and spin periods

Many characteristics of dwarf carbon stars are broadly consistent with a binary origin, including mass transfer from an evolved companion. While the population overall appears to have old-disc or halo kinematics, roughly 2 per cent of these stars exhibit Hα emission, which in low-mass main-sequence stars is generally associated with rotation and relative youth. Its presence in an older population therefore suggests either irradiation or spin-up. […]

October 2021: Whitehouse, L. J., Farihi, J., Howarth, I. D., Mancino, S., Walters, N., et al (Monthly Notices of the Royal Astronomical Society)

Unbiased likelihood-free inference of the Hubble constant from light standard sirens

Multimessenger observations of binary neutron star mergers offer a promising path toward resolution of the Hubble constant (H₀) tension, provided their constraints are shown to be free from systematics such as the Malmquist bias. In the traditional Bayesian framework, accounting for selection effects in the likelihood requires calculation of the expected number (or fraction) of detections as a function of the parameters describing the population and cosmology; a potentially costly and/or inaccurate process. This calculation can, however, be bypassed completely by performing the inference in a framework in which the likelihood is never explicitly calculated, but instead fit using forward simulations of the data, which naturally include the selection. […]

October 2021: Gerardi, Francesca, Feeney, Stephen M., Alsing, Justin (Physical Review D)

SUPER. V. ALMA continuum observations of z ∼ 2 AGN and the elusive evidence of outflows influencing star formation

We study the impact of active galactic nuclei (AGN) ionised outflows on star formation in high-redshift AGN host galaxies, by combining near-infrared integral field spectroscopic (IFS) observations, mapping the Hα emission and [O III]λ5007 outflows, with matched-resolution observations of the rest-frame far-infrared (FIR) emission. We present high-resolution ALMA Band 7 observations of eight X-ray selected AGN (L_{2 − 10 keV} = 10^43.8 − 10^45.2 erg s⁻¹) at z ∼ 2 from the SUPER (SINFONI Survey for Unveiling the Physics and Effect of Radiative feedback) sample, targeting the observed-frame 870 μm (rest-frame ∼260 μm) continuum at ∼2 kpc (0.2″) spatial resolution. The targets were selected among the SUPER AGN with an [O III] detection in the IFS maps and with a detection in the FIR photometry. […]

October 2021: Lamperti, I., Harrison, C. M., Mainieri, V., Kakkad, D., Perna, M., et al (Astronomy and Astrophysics)

Cosmology beyond BAO from the 3D distribution of the Lyman-α forest

We propose a new method for fitting the full-shape of the Lyman-α (Ly α) forest 3D correlation function in order to measure the Alcock-Paczynski (AP) effect. Our method preserves the robustness of baryon acoustic oscillations (BAO) analyses, while also providing extra cosmological information from a broader range of scales. We compute idealized forecasts for the Dark Energy Spectroscopic Instrument (DESI) using the Ly α autocorrelation and its cross-correlation with quasars, and show how this type of analysis improves cosmological constraints. […]

October 2021: Cuceu, Andrei, Font-Ribera, Andreu, Joachimi, Benjamin, Nadathur, Seshadri (Monthly Notices of the Royal Astronomical Society)

Evidence for sub-Chandrasekhar Type Ia supernovae from the last major merger

We investigate the contribution of sub-Chandrasekhar mass Type Ia supernovae to the chemical enrichment of the Gaia Sausage galaxy, the progenitor of a significant merger event in the early life of the Milky Way. Using a combination of data from Nissen & Schuster, the GALactic Archaeology with HERMES (GALAH) Data Release 3 [with 1D non-local thermal equilibrium (NLTE) abundance corrections], and the Apache Point Observatory Galactic Evolution Experiment (APOGEE) Data Release 16, we fit analytic chemical evolution models to a nine-dimensional chemical abundance space (Fe, Mg, Si, Ca, Cr, Mn, Ni, Cu, and Zn) in particular focusing on the iron-peak elements, Mn and Ni. We find that low [Mn/Fe] $\sim -0.15\, \mathrm{dex}$ and low [Ni/Fe] $\sim -0.3\, \mathrm{dex}$ Type Ia yields are required to explain the observed trends beyond the [α/Fe] knee of the Gaia Sausage (approximately at [Fe/H] $=-1.4\, \mathrm{dex}$). […]

September 2021: Sanders, Jason L., Belokurov, Vasily, Man, Kai T. F. (Monthly Notices of the Royal Astronomical Society)

Disentangling atmospheric compositions of K2-18 b with next generation facilities

Recent analysis of the planet K2-18 b has shown the presence of water vapour in its atmosphere. While the H₂O detection is significant, the Hubble Space Telescope (HST) WFC3 spectrum suggests three possible solutions of very different nature which can equally match the data. The three solutions are a primary cloudy atmosphere with traces of water vapour (cloudy sub-Neptune), a secondary atmosphere with a substantial amount (up to 50% Volume Mixing Ratio) of H₂O (icy/water world) and/or an undetectable gas such as N₂ (super-Earth). […]

September 2021: Changeat, Quentin, Edwards, Billy, Al-Refaie, Ahmed F., Tsiaras, Angelos, Waldmann, Ingo P., et al (Experimental Astronomy)

Full-sky integrated Sachs-Wolfe maps for the MICE grand challenge lightcone simulation

We present full-sky maps of the Integrated Sachs-Wolfe effect (ISW) for the MICE Grand Challenge lightcone simulation up to redshift 1.4. The maps are constructed in the linear regime using spherical Bessel transforms. We compare and contrast this procedure against analytical approximations found in the literature. […]

September 2021: Naidoo, Krishna, Fosalba, Pablo, Whiteway, Lorne, Lahav, Ofer (Monthly Notices of the Royal Astronomical Society)

Chemulator: Fast, accurate thermochemistry for dynamical models through emulation

Context. Chemical modelling serves two purposes in dynamical models: accounting for the effect of microphysics on the dynamics and providing observable signatures. Ideally, the former must be done as part of the hydrodynamic simulation but this comes with a prohibitive computational cost that leads to many simplifications being used in practice. […]

September 2021: Holdship, J., Viti, S., Haworth, T. J., Ilee, J. D. (Astronomy and Astrophysics)

Collisions in a gas-rich white dwarf planetary debris disc

WD 0145+234 is a white dwarf that is accreting metals from a circumstellar disc of planetary material. It has exhibited a substantial and sustained increase in 3-5 $\mu$m flux since 2018. Follow-up Spitzer photometry reveals that emission from the disc had begun to decrease by late 2019. […]

September 2021: Swan, Andrew, Kenyon, Scott J., Farihi, Jay, Dennihy, Erik, Gänsicke, Boris T., et al (Monthly Notices of the Royal Astronomical Society)

Gravitons in a box

Gravity and matter are universally coupled, and this unique universality provides us with an intriguing way to quantify quantum aspects of space-time in terms of the number of gravitons within a given box. In particular, we provide a limit on the number of gravitons if we trace out the matter degrees of freedom. We obtain the universal bound on the number of gravitons, which would be given by N_g≈(m /M_p)². […]

September 2021: Bose, Sougato, Mazumdar, Anupam, Toroš, Marko (Physical Review D)

Benchmarking and scalability of machine-learning methods for photometric redshift estimation

Obtaining accurate photometric redshift (photo-z) estimations is an important aspect of cosmology, remaining a prerequisite of many analyses. In creating novel methods to produce photo-z estimations, there has been a shift towards using machine-learning techniques. However, there has not been as much of a focus on how well different machine-learning methods scale or perform with the ever-increasing amounts of data being produced. […]

August 2021: Henghes, Ben, Pettitt, Connor, Thiyagalingam, Jeyan, Hey, Tony, Lahav, Ofer (Monthly Notices of the Royal Astronomical Society)

The VANDELS Survey: new constraints on the high-mass X-ray binary populations in normal star-forming galaxies at 3 < z < 5.5

We use VANDELS spectroscopic data overlapping with the ≃7 Ms Chandra Deep Field South survey to extend studies of high-mass X-ray binary systems (HMXBs) in 301 normal star-forming galaxies in the redshift range 3 < z < 5.5. Our analysis evaluates correlations between X-ray luminosities (L_X), star formation rates (SFRs), and stellar metallicities (Z_⋆) to higher redshifts and over a wider range in galaxy properties than hitherto. Using a stacking analysis performed in bins of both redshift and SFR for sources with robust spectroscopic redshifts without AGN signatures, we find convincing evolutionary trends in the ratio L_X/SFR to the highest redshifts probed, with a stronger trend for galaxies with lower SFRs. […]

August 2021: Saxena, A., Ellis, R. S., Förster, P. U., Calabrò, A., Pentericci, L., et al (Monthly Notices of the Royal Astronomical Society)

Dark Energy Survey Year 3 results: Curved-sky weak lensing mass map reconstruction

We present reconstructed convergence maps, mass maps, from the Dark Energy Survey (DES) third year (Y3) weak gravitational lensing data set. The mass maps are weighted projections of the density field (primarily dark matter) in the foreground of the observed galaxies. We use four reconstruction methods, each is a maximum a posteriori estimate with a different model for the prior probability of the map: Kaiser-Squires, null B-mode prior, Gaussian prior, and a sparsity prior. […]

August 2021: Jeffrey, N., Gatti, M., Chang, C., Whiteway, L., Demirbozan, U., et al (Monthly Notices of the Royal Astronomical Society)

TauREx 3: A Fast, Dynamic, and Extendable Framework for Retrievals

TauREx 3 is the next generation of the TauREx exoplanet atmospheric retrieval framework for Windows, Mac, and Linux. It is a complete rewrite with a full Python stack that makes it easy-to-use, high-performance, dynamic, and flexible. The new main TauREx program is built with modularity in mind, allowing the user to augment its functionalities with custom code and efficiently perform retrievals on custom parameters. […]

August 2021: Al-Refaie, A. F., Changeat, Q., Waldmann, I. P., Tinetti, G. (The Astrophysical Journal)

Assessing tension metrics with dark energy survey and Planck data

Quantifying tensions - inconsistencies amongst measurements of cosmological parameters by different experiments - has emerged as a crucial part of modern cosmological data analysis. Statistically significant tensions between two experiments or cosmological probes may indicate new physics extending beyond the standard cosmological model and need to be promptly identified. We apply several tension estimators proposed in the literature to the dark energy survey (DES) large-scale structure measurement and Planck cosmic microwave background data. […]

August 2021: Lemos, P., Raveri, M., Campos, A., Park, Y., Chang, C., et al (Monthly Notices of the Royal Astronomical Society)

Revealing the Physical Conditions around Sgr A* Using Bayesian Inference. I. Observations and Radiative Transfer

We report subarcsecond Atacama Large Millimeter/submillimeter Array (ALMA) observations between 272 and 375 GHz toward Sgr A*'s circumnuclear disk (CND). Our data comprise eight individual pointings, with significant SiO (8₇-7₆) and SO (7-6) emission detected toward 98 positions within these pointings. Additionally, we identify H₂CS (9_1,9-8_1,8), OCS (25-24), and CH₃OH (2_1,1-2_0,2) toward a smaller subset of positions. […]

August 2021: James, Tomas A., Viti, Serena, Yusef-Zadeh, Farhad, Royster, Marc, Wardle, Mark (The Astrophysical Journal)

ExoMol molecular line lists - XLII. Rovibronic molecular line list for the low-lying states of NO

An accurate line list, called XABC, is computed for nitric oxide which covers its pure rotational, vibrational and rovibronic spectra. A mixture of empirical and theoretical electronic transition dipole moments are used for the final calculation of ¹⁴N¹⁶O rovibronic $\mathrm{A}\, ^2\Sigma ^+$ - $\mathrm{X}\, ^2\Pi$, $\mathrm{B}\, ^2\Pi$ - X²Π, and $\mathrm{C}\, ^2\Pi$ - $\mathrm{X}\, ^2\Pi$ which correspond to the γ, β, and δ band systems, respectively, as well as minor improvements to transitions within the $\mathrm{X}\, ^2\Pi$ ground state. The work is a major update of the ExoMol NOname line list. […]

July 2021: Qu, Qianwei, Yurchenko, Sergei N., Tennyson, Jonathan (Monthly Notices of the Royal Astronomical Society)

Constraints on the dust extinction law of the Galaxy with Swift/UVOT, Gaia, and 2MASS

We explore variations of the dust extinction law of the Milky Way by selecting stars from the Swift/UVOT Serendipitous Source Catalogue, cross-matched with Gaia DR2 and 2MASS to produce a sample of 10 452 stars out to ~4 kpc with photometry covering a wide spectral window. The near ultraviolet passbands optimally encompass the 2175 Å bump, so that we can simultaneously fit the net extinction, quoted in the V band (A_V), the steepness of the wavelength dependence (δ), and the bump strength (E_b). The methodology compares the observed magnitudes with theoretical stellar atmospheres from the models of Coelho. […]

July 2021: Ferreras, Ignacio, Tress, Mónica, Bruzual, Gustavo, Charlot, Stéphane, Page, Mat, et al (Monthly Notices of the Royal Astronomical Society)

Original Research by Young Twinkle Students (ORBYTS): ephemeris refinement of transiting exoplanets

We report follow-up observations of transiting exoplanets that have either large uncertainties (>10 min) in their transit times or have not been observed for over 3 yr. A fully robotic ground-based telescope network, observations from citizen astronomers, and data from TESS have been used to study eight planets, refining their ephemerides and orbital data. Such follow-up observations are key for ensuring accurate transit times for upcoming ground- and space-based telescopes, which may seek to characterize the atmospheres of these planets. […]

July 2021: Edwards, Billy, Changeat, Quentin, Yip, Kai Hou, Tsiaras, Angelos, Taylor, Jake, et al (Monthly Notices of the Royal Astronomical Society)

The dust mass in Cassiopeia A from infrared and optical line flux differences

The large quantities of dust that have been found in a number of high-redshift galaxies have led to suggestions that core-collapse supernovae (CCSNe) are the main sources of their dust and have motivated the measurement of the dust masses formed by local CCSNe. For Cassiopeia A (Cas A), an oxygen-rich remnant of a Type IIb CCSN, a dust mass of 0.6-1.1 M_⊙ has already been determined by two different methods, namely (a) from its far-infrared spectral energy distribution and (b) from analysis of the red-blue emission line asymmetries in its integrated optical spectrum. We present a third, independent, method for determining the mass of dust contained within Cas A. […]

June 2021: Niculescu-Duvaz, Maria, Barlow, M. J., Bevan, A., Milisavljevic, D., De Looze, I. (Monthly Notices of the Royal Astronomical Society)

Magnification bias in galaxy surveys with complex sample selection functions

Gravitational lensing magnification modifies the observed spatial distribution of galaxies and can severely bias cosmological probes of large-scale structure if not accurately modelled. Standard approaches to modelling this magnification bias may not be applicable in practice as many galaxy samples have complex, often implicit, selection functions. We propose and test a procedure to quantify the magnification bias induced in clustering and galaxy-galaxy lensing (GGL) signals in galaxy samples subject to a selection function beyond a simple flux limit. […]

June 2021: von Wietersheim-Kramsta, Maximilian, Joachimi, Benjamin, van den Busch, Jan Luca, Heymans, Catherine, Hildebrandt, Hendrik, et al (Monthly Notices of the Royal Astronomical Society)

Terminus: A Versatile Simulator for Space-based Telescopes

Space-based telescopes offer unparalleled opportunities for characterizing exoplanets, solar system bodies, and stellar objects. However, observatories in low-Earth orbits (e.g., Hubble, CHaracterising ExOPlanets Satellite, Twinkle, and an ever-increasing number of cubesats) cannot always be continuously pointed at a target due to Earth obscuration. For exoplanet observations consisting of transit, or eclipse, spectroscopy, this causes gaps in the light curve, which reduces the information content and can diminish the science return of the observation. […]

June 2021: Edwards, Billy, Stotesbury, Ian (The Astronomical Journal)

Self-calibration and robust propagation of photometric redshift distribution uncertainties in weak gravitational lensing

We present a method that accurately propagates residual uncertainties in photometric redshift distributions into the cosmological inference from weak lensing measurements. The redshift distributions of tomographic redshift bins are parameterised using a flexible modified Gaussian mixture model. We fit this model to pre-calibrated redshift distributions and implement an analytic marginalisation over the potentially several hundred redshift nuisance parameters in the weak lensing likelihood, which is demonstrated to accurately recover the cosmological posterior. […]

June 2021: Stölzner, B., Joachimi, B., Korn, A., Hildebrandt, H., Wright, A. H. (Astronomy and Astrophysics)

Chronos: A NIR spectroscopic galaxy survey to probe the most fundamental stages of galaxy evolution

We propose a dedicated, ultra-deep spectroscopic survey in the near infrared (NIR), that will target a mass-limited sample of galaxies during two of the most fundamental epochs of cosmic evolution: the formation of the first galaxies (at z ≳ 6; cosmic dawn), and at the peak of galaxy formation activity (at redshift z∼1-3; cosmic noon). By way of NIR observations (λ= 0.8-2μ m), it is possible to study the UV Lyman-α region in the former, and the optical rest-frame in the latter, allowing us to extract fundamental observables such as gas and stellar kinematics, chemical abundances, and ages, providing a unique legacy database covering these two crucial stages of cosmic evolution. The need to work in the NIR at extremely low flux levels makes a ground-based approach unfeasible due to atmospheric emission and absorption. […]

June 2021: Ferreras, I., Cropper, M., Sharples, R., Bland-Hawthorn, J., Bruzual, G., et al (Experimental Astronomy)

A test of the planet-star unipolar inductor for magnetic white dwarfs

Despite thousands of spectroscopic detections, only four isolated white dwarfs exhibit Balmer emission lines. The temperature inversion mechanism is a puzzle over 30 years old that has defied conventional explanations. One hypothesis is a unipolar inductor that achieves surface heating via ohmic dissipation of a current loop between a conducting planet and a magnetic white dwarf. […]

May 2021: Walters, N., Farihi, J., Marsh, T. R., Bagnulo, S., Landstreet, J. D., et al (Monthly Notices of the Royal Astronomical Society)

Fine structure of type III solar radio bursts from Langmuir wave motion in turbulent plasma

The Sun frequently accelerates near-relativistic electron beams that travel out through the solar corona and interplanetary space. Interacting with their plasma environment, these beams produce type III radio bursts—the brightest astrophysical radio sources seen from Earth. The formation and motion of type III fine frequency structures is a puzzle, but is commonly believed to be related to plasma turbulence in the solar corona and solar wind. […]

May 2021: Reid, Hamish A. S., Kontar, Eduard P. (Nature Astronomy)

Electron Bulk Heating at Saturn's Magnetopause

Magnetic reconnection at the magnetopause (MP) energizes ambient plasma via the release of magnetic energy and produces an "open" magnetosphere allowing solar wind particles to directly enter the system. At Saturn, the nature of MP reconnection remains unclear. The current study examines electron bulk heating at MP crossings, in order to probe the relationship between observed and predicted reconnection heating proposed by Phan et al. […]

May 2021: Cheng, I., Achilleos, N., Masters, A., Lewis, G., Kane, M., et al (Journal of Geophysical Research (Space Physics))

An emulator for the Lyman-α forest in beyond-ΛCDM cosmologies

Interpreting observations of the Lyman-α forest flux power spectrum requires interpolation between a small number of expensive simulations. We present a Gaussian process emulator modelling the 1D flux power spectrum as a function of the amplitude and slope of the small-scale linear matter power spectrum, and the state of the intergalactic medium at the epoch of interest (2 < z < 4). This parameterisation enables the prediction of the flux power spectrum in extended cosmological models that are not explicitly included in the training set, eliminating the need to construct bespoke emulators for a number of extensions to ΛCDM. […]

May 2021: Pedersen, Christian, Font-Ribera, Andreu, Rogers, Keir K., McDonald, Patrick, Peiris, Hiranya V., et al (Journal of Cosmology and Astroparticle Physics)

The PAU Survey: narrow-band photometric redshifts using Gaussian processes

We study the performance of the hybrid template machine learning photometric redshift (photo-z) algorithm DELIGHT, which uses Gaussian processes, on a subset of the early data release of the Physics of the Accelerating Universe Survey (PAUS). We calibrate the fluxes of the 40 PAUS narrow bands with six broad-band fluxes (uBVriz) in the Cosmic Evolution Survey (COSMOS) field using three different methods, including a new method that utilizes the correlation between the apparent size and overall flux of the galaxy. We use a rich set of empirically derived galaxy spectral templates as guides to train the Gaussian process, and we show that our results are competitive with other standard photometric redshift algorithms. […]

May 2021: Soo, John Y. H., Joachimi, Benjamin, Eriksen, Martin, Siudek, Małgorzata, Alarcon, Alex, et al (Monthly Notices of the Royal Astronomical Society)

Disentangled Representation Learning for Astronomical Chemical Tagging

Modern astronomical surveys are observing spectral data for millions of stars. These spectra contain chemical information that can be used to trace the Galaxy's formation and chemical enrichment history. However, extracting the information from spectra and making precise and accurate chemical abundance measurements is challenging. […]

May 2021: de Mijolla, Damien, Ness, Melissa Kay, Viti, Serena, Wheeler, Adam Joseph (The Astrophysical Journal)

Self-calibration of weak lensing systematic effects using combined two- and three-point statistics

We investigate the prospects for using the weak lensing bispectrum alongside the power spectrum to control systematic uncertainties in a Euclid-like survey. Three systematic effects are considered: the intrinsic alignment of galaxies, uncertainties in the means of tomographic redshift distributions, and multiplicative bias in the measurement of the shear signal. We find that the bispectrum is very effective in mitigating these systematic errors. […]

May 2021: Pyne, Susan, Joachimi, Benjamin (Monthly Notices of the Royal Astronomical Society)

An Exploration of Model Degeneracies with a Unified Phase Curve Retrieval Analysis: The Light and Dark Sides of WASP-43 b

The analysis of exoplanetary atmospheres often relies upon the observation of transit or eclipse events. While very powerful, these snapshots provide mainly one-dimensional information on the planet structure and do not easily allow precise latitude-longitude characterizations. The phase curve technique, which consists of measuring the planet emission throughout its entire orbit, can break this limitation and provide useful two-dimensional thermal and chemical constraints on the atmosphere. […]

May 2021: Changeat, Q., Al-Refaie, A. F., Edwards, B., Waldmann, I. P., Tinetti, G. (The Astrophysical Journal)

An improved rovibrational linelist of formaldehyde, H₂¹² C¹⁶O

Published high-resolution rotation-vibration transitions of H₂¹²C¹⁶O, the principal isotopologue of methanal, are analyzed using the MARVEL (Measured Active Rotation-Vibration Energy Levels) procedure. The literature results are augmented by new, high-accuracy measurements of pure rotational transitions within the ground, ν₃ , ν₄ , and ν₆ vibrational states. Of the 16 596 non-redundant transitions processed, which come from 43 sources including the present work, 16 403 could be validated, providing 5029 empirical energy levels of H₂¹²C¹⁶O with statistically well-defined uncertainties. […]

May 2021: Al-Derzi, Afaf R., Tennyson, Jonathan, Yurchenko, Sergei N., Melosso, Mattia, Jiang, Ningjing, et al (Journal of Quantitative Spectroscopy and Radiative Transfer)

Lyman-alpha spectroscopy of extreme [O III] emitting galaxies at z ≃ 2-3: implications for Lyα visibility and LyC leakage at z > 6

Spectroscopic observations of massive z > 7 galaxies selected to have extremely large [O III] + H β equivalent width (EW ~1500 Å) have recently revealed large Ly α detection rates, in contrast to the weak emission seen in the general population. Why these systems are uniquely visible in Ly α at redshifts where the intergalactic medium (IGM) is likely significantly neutral is not clear. With the goal of better understanding these results, we have begun a campaign with MMT and Magellan to measure Ly α in galaxies with similar [O III] + H β EWs at z ≃ 2-3. […]

May 2021: Tang, Mengtao, Stark, Daniel P., Chevallard, Jacopo, Charlot, Stéphane, Endsley, Ryan, et al (Monthly Notices of the Royal Astronomical Society)

A comparison of quasar emission reconstruction techniques for z ≥ 5.0 Lyman α and Lyman β transmission

Reconstruction techniques for intrinsic quasar continua are crucial for the precision study of Lyman α (Ly α) and Lyman β (Ly β) transmission at z > 5.5, where the λ < 1215 Å emission of quasars is nearly completely absorbed. While the number and quality of spectroscopic observations have become theoretically sufficient to quantify Ly α transmission at 5.0 < z < 6.0 to better than $1{{\ \rm per\ cent}}$, the biases and uncertainties arising from predicting the unabsorbed continuum are not known to the same level. In this paper, we systematically evaluate eight reconstruction techniques on a unified testing sample of 2.7 < z < 3.5 quasars drawn from the Extended Baryon Oscillation Spectroscopic Survey. […]

May 2021: Bosman, Sarah E. I., Ďurovčíková, Dominika, Davies, Frederick B., Eilers, Anna-Christina (Monthly Notices of the Royal Astronomical Society)

Organised randoms: Learning and correcting for systematic galaxy clustering patterns in KiDS using self-organising maps

We present a new method for the mitigation of observational systematic effects in angular galaxy clustering through the use of corrective random galaxy catalogues. Real and synthetic galaxy data from the Kilo Degree Survey's (KiDS) 4th Data Release (KiDS-1000) and the Full-sky Lognormal Astro-fields Simulation Kit package, respectively, are used to train self-organising maps to learn the multivariate relationships between observed galaxy number density and up to six systematic-tracer variables, including seeing, Galactic dust extinction, and Galactic stellar density. We then create `organised' randoms; random galaxy catalogues with spatially variable number densities, mimicking the learnt systematic density modes in the data. […]

April 2021: Johnston, Harry, Wright, Angus H., Joachimi, Benjamin, Bilicki, Maciej, Elisa Chisari, Nora, et al (Astronomy and Astrophysics)

Erratum: Evaluating hydrodynamical simulations with green valley galaxies

April 2021: Angthopo, J., Negri, A., Ferreras, I., de la Rosa, I. G., Vecchia, C. Dalla, et al (Monthly Notices of the Royal Astronomical Society)

Angular momentum evolution can be predicted from cosmological initial conditions

The angular momentum of dark matter haloes controls their spin magnitude and orientation, which in turn influences the galaxies therein. However, the process by which dark matter haloes acquire angular momentum is not fully understood; in particular, it is unclear whether angular momentum growth is stochastic. To address this question, we extend the genetic modification technique to allow control over the angular momentum of any region in the initial conditions. […]

April 2021: Cadiou, Corentin, Pontzen, Andrew, Peiris, Hiranya V. (Monthly Notices of the Royal Astronomical Society)

Prospects for Measuring the Hubble Constant with Neutron-Star-Black-Hole Mergers

Gravitational wave (GW) and electromagnetic (EM) observations of neutron-star-black-hole (NSBH) mergers can provide precise local measurements of the Hubble constant (H₀), ideal for resolving the current H₀ tension. We perform end-to-end analyses of realistic populations of simulated NSBHs, incorporating both GW and EM selection for the first time. We show that NSBHs could achieve unbiased 1.5%-2.4% precision H₀ estimates by 2030. […]

April 2021: Feeney, Stephen M., Peiris, Hiranya V., Nissanke, Samaya M., Mortlock, Daniel J. (Physical Review Letters)

Phase-curve Pollution of Exoplanet Transmission Spectra

The occurrence of a planet transiting in front of its host star offers the opportunity to observe the planet's atmosphere filtering starlight. The fraction of occulted stellar flux is roughly proportional to the optically thick area of the planet, the extent of which depends on the opacity of the planet's gaseous envelope at the observed wavelengths. Chemical species, haze, and clouds are now routinely detected in exoplanet atmospheres through rather small features in transmission spectra, i.e., collections of planet-to-star area ratios across multiple spectral bins and/or photometric bands. […]

April 2021: Morello, Giuseppe, Zingales, Tiziano, Martin-Lagarde, Marine, Gastaud, René, Lagage, Pierre-Olivier (The Astronomical Journal)

A machine learning approach to galaxy properties: joint redshift-stellar mass probability distributions with Random Forest

We demonstrate that highly accurate joint redshift-stellar mass probability distribution functions (PDFs) can be obtained using the Random Forest (RF) machine learning (ML) algorithm, even with few photometric bands available. As an example, we use the Dark Energy Survey (DES), combined with the COSMOS2015 catalogue for redshifts and stellar masses. We build two ML models: one containing deep photometry in the griz bands, and the second reflecting the photometric scatter present in the main DES survey, with carefully constructed representative training data in each case. […]

April 2021: Mucesh, S., Hartley, W. G., Palmese, A., Lahav, O., Whiteway, L., et al (Monthly Notices of the Royal Astronomical Society)

Evaluating hydrodynamical simulations with green valley galaxies

We test cosmological hydrodynamical simulations of galaxy formation regarding the properties of the blue cloud (BC), green valley (GV), and red sequence (RS), as measured on the 4000Å break strength versus stellar mass plane at z = 0.1. We analyse the RefL0100N1504 run of EAGLE and the TNG100 run of IllustrisTNG project, by comparing them with the Sloan Digital Sky Survey (SDSS), while taking into account selection bias. Our analysis focuses on the GV, within stellar mass $\log \, \mathrm{{\it M}_\star /M_{\odot }} \simeq 10\!-\!11$ , selected from the bimodal distribution of galaxies on the D_n(4000) versus stellar mass plane, following Angthopo et al. […]

April 2021: Angthopo, J., Negri, A., Ferreras, I., de la Rosa, I. G., Dalla Vecchia, C., et al (Monthly Notices of the Royal Astronomical Society)

SSSpaNG! stellar spectra as sparse, data-driven, non-Gaussian processes

Upcoming million-star spectroscopic surveys have the potential to revolutionize our view of the formation and chemical evolution of the Milky Way. Realizing this potential requires automated approaches to optimize estimates of stellar properties, such as chemical element abundances, from the spectra. The sheer volume and quality of the observations strongly motivate that these approaches should be driven by the data. […]

March 2021: Feeney, Stephen M., Wandelt, Benjamin D., Ness, Melissa K. (Monthly Notices of the Royal Astronomical Society)

Quantifying the global parameter tensions between ACT, SPT, and Planck

The overall cosmological parameter tension between the Atacama Cosmology Telescope 2020 fourth data release (ACT) and Planck 2018 data within the concordance cosmological model is quantified using the Suspiciousness statistic to be 2.6 σ . Between ACT and the South Pole Telescope (SPT) we find a tension of 2.4 σ , and 2.8 σ between ACT and Planck +SPT combined. While it is unclear whether the tension is caused by statistical fluctuations, systematic effects or new physics, caution should be exercised in combining these cosmic microwave background datasets in the context of the Λ CDM standard model of the universe.

March 2021: Handley, Will, Lemos, Pablo (Physical Review D)

Hydrodynamic escape of mineral atmosphere from hot rocky exoplanet. I. Model description

Recent exoplanet statistics indicate that photo-evaporation has a great impact on the mass and bulk composition of close-in low-mass planets. While there are many studies addressing photo-evaporation of hydrogen- or water-rich atmospheres, no detailed investigation regarding rocky vapour atmospheres (or mineral atmospheres) has been conducted. Here, we develop a new 1D hydrodynamic model of the ultraviolet (UV)-irradiated mineral atmosphere composed of Na, Mg, O, Si, their ions and electrons, including molecular diffusion, thermal conduction, photo-/thermochemistry, X-ray and UV heating, and radiative line cooling (i.e. […]

March 2021: Ito, Yuichi, Ikoma, Masahiro (Monthly Notices of the Royal Astronomical Society)

ExoMol line lists - XLI. High-temperature molecular line lists for the alkali metal hydroxides KOH and NaOH

Potassium hydroxide (KOH) and sodium hydroxide (NaOH) are expected to occur in the atmospheres of hot rocky super-Earth exoplanets but a lack of spectroscopic data is hampering their potential detection. Using robust first-principles methodologies, comprehensive molecular line lists for KOH and NaOH that are applicable for temperatures up to T = 3500 K are presented. The KOH OYT4 line list covers the 0-6000 cm^-1 (wavelengths λ > 1.67 µm) range and comprises 38 billion transitions between 7.3 million energy levels with rotational excitation up to J = 255. […]

March 2021: Owens, A., Tennyson, J., Yurchenko, S. N. (Monthly Notices of the Royal Astronomical Society)

Constraining cosmology using galaxy position angle-only cosmic shear

We investigate cosmological parameter inference from realistic simulated weak lensing image data using only galaxy position angles, as opposed to full-ellipticity information. We demonstrate that input shear fields can be accurately reconstructed using only the statistics of source galaxy position angles and that, from these shear fields, we can successfully recover power spectra and infer the input cosmology. This paper builds on previous work on angle-only weak lensing estimation by extending the method to deal with variable and anisotropic point spread function (PSF) convolution and variable shear fields. […]

March 2021: Whittaker, Lee (Monthly Notices of the Royal Astronomical Society)

H α fluxes and extinction distances for planetary nebulae in the IPHAS survey of the northern galactic plane

We report H α filter photometry for 197 Northern hemisphere planetary nebulae (PNe) obtained using imaging data from the IPHAS survey. H α+[N II] fluxes were measured for 46 confirmed or possible PNe discovered by the IPHAS survey and for 151 previously catalogued PNe that fell within the area of the northern Galactic Plane surveyed by IPHAS. After correcting for [N II] emission admitted by the IPHAS H α filter, the resulting H α fluxes were combined with published radio free-free fluxes and H β fluxes, in order to estimate mean optical extinctions to 143 PNe using ratios involving their integrated Balmer line fluxes and their extinction-free radio fluxes. […]

March 2021: Dharmawardena, Thavisha E., Barlow, M. J., Drew, J. E., Seales, A., Sale, S. E., et al (Monthly Notices of the Royal Astronomical Society)

PyLightcurve-torch: a transit modeling package for deep learning applications in PyTorch

We present a new open source python package, based on PyLightcurve and PyTorch Paszke et al., tailored for efficient computation and automatic differentiation of exoplanetary transits. The classes and functions implemented are fully vectorised, natively GPU-compatible and differentiable with respect to the stellar and planetary parameters. This makes PyLightcurve-torch suitable for traditional forward computation of transits, but also extends the range of possible applications with inference and optimization algorithms requiring access to the gradients of the physical model. […]

March 2021: Morvan, Mario, Tsiaras, Angelos, Nikolaou, Nikolaos, Waldmann, Ingo P. (Publications of the Astronomical Society of the Pacific)

Group-scale intrinsic galaxy alignments in the Illustris-TNG and MassiveBlack-II simulations

We study the alignments of satellite galaxies, and their anisotropic distribution, with respect to location and orientation of their host central galaxy in MassiveBlack-II (MB-II) and IllustrisTNG simulations. We find that: the shape of the satellite system in haloes of mass ($\gt 10^{13}\, h^{-1}\, \mathrm{M}_{\odot }$) is well aligned with the shape of the central galaxy at z = 0.06 with the mean alignment between the major axes being ~Δθ = 12° when compared to a uniform random distribution; that satellite galaxies tend to be anisotropically distributed along the major axis of the central galaxy with a stronger alignment in haloes of higher mass or luminosity; and that the satellite distribution is more anisotropic for central galaxies with lower star formation rate, which are spheroidal, and for red central galaxies. Radially, we find that satellites tend to be distributed along the major axis of the shape of the stellar component of central galaxies at smaller scales and the dark matter component on larger scales. […]

March 2021: Tenneti, Ananth, Kitching, Thomas D., Joachimi, Benjamin, Di Matteo, Tiziana (Monthly Notices of the Royal Astronomical Society)

The PAU Survey: Intrinsic alignments and clustering of narrow-band photometric galaxies

We present the first measurements of the projected clustering and intrinsic alignments (IA) of galaxies observed by the Physics of the Accelerating Universe Survey (PAUS). With photometry in 40 narrow optical passbands (4500 Å-8500 Å), the quality of photometric redshift estimation is σ_z ∼ 0.01(1 + z) for galaxies in the 19 deg² Canada-France-Hawaii Telescope Legacy Survey W3 field, allowing us to measure the projected 3D clustering and IA for flux-limited, faint galaxies (i < 22.5) out to z ∼ 0.8. To measure two-point statistics, we developed, and tested with mock photometric redshift samples, `cloned' random galaxy catalogues which can reproduce data selection functions in 3D and account for photometric redshift errors. […]

February 2021: Johnston, Harry, Joachimi, Benjamin, Norberg, Peder, Hoekstra, Henk, Eriksen, Martin, et al (Astronomy and Astrophysics)

The cosmic abundance of cold gas in the local Universe

We determine the cosmic abundance of molecular hydrogen (H₂) in the local Universe from the xCOLD GASS survey. To constrain the H₂ mass function at low masses and correct for the effect of the lower stellar mass limit of $10^9 \, \mathrm{M}_{\odot }$ in the xCOLD GASS survey, we use an empirical approach based on an observed scaling relation between star formation rate and gas mass. We also constrain the H I and H I+H₂ mass functions using the xGASS survey and compare them to the H I mass function from the ALFALFA survey. […]

February 2021: Fletcher, Thomas J., Saintonge, Amélie, Soares, Paula S., Pontzen, Andrew (Monthly Notices of the Royal Astronomical Society)

EDGE: a new approach to suppressing numerical diffusion in adaptive mesh simulations of galaxy formation

We introduce a new method to mitigate numerical diffusion in adaptive mesh refinement (AMR) simulations of cosmological galaxy formation, and study its impact on a simulated dwarf galaxy as part of the 'EDGE' project. The target galaxy has a maximum circular velocity of $21\, \mathrm{km}\, \mathrm{s}^{-1}$ but evolves in a region that is moving at up to $90\, \mathrm{km}\, \mathrm{s}^{-1}$ relative to the hydrodynamic grid. In the absence of any mitigation, diffusion softens the filaments feeding our galaxy. […]

February 2021: Pontzen, Andrew, Rey, Martin P., Cadiou, Corentin, Agertz, Oscar, Teyssier, Romain, et al (Monthly Notices of the Royal Astronomical Society)

Likelihood-free inference with neural compression of DES SV weak lensing map statistics

In many cosmological inference problems, the likelihood (the probability of the observed data as a function of the unknown parameters) is unknown or intractable. This necessitates approximations and assumptions, which can lead to incorrect inference of cosmological parameters, including the nature of dark matter and dark energy, or create artificial model tensions. Likelihood-free inference covers a novel family of methods to rigorously estimate posterior distributions of parameters using forward modelling of mock data. […]

February 2021: Jeffrey, Niall, Alsing, Justin, Lanusse, François (Monthly Notices of the Royal Astronomical Society)

GenetIC—A New Initial Conditions Generator to Support Genetically Modified Zoom Simulations

We present genetIC, a new code for generating initial conditions for cosmological N-body simulations. The code allows precise, user-specified alterations to be made to arbitrary regions of the simulation (while maintaining consistency with the statistical ensemble). These "genetic modifications" allow, for example, the history, mass, or environment of a target halo to be altered in order to study the effect on their evolution. […]

February 2021: Stopyra, Stephen, Pontzen, Andrew, Peiris, Hiranya, Roth, Nina, Rey, Martin P. (The Astrophysical Journal Supplement Series)

SUPER. IV. CO(J = 3-2) properties of active galactic nucleus hosts at cosmic noon revealed by ALMA

Feedback from active galactic nuclei (AGN) is thought to be key in shaping the life cycle of their host galaxies by regulating star-formation activity. Therefore, to understand the impact of AGN on star formation, it is essential to trace the molecular gas out of which stars form. In this paper we present the first systematic study of the CO properties of AGN hosts at z ≈ 2 for a sample of 27 X-ray selected AGN spanning two orders of magnitude in AGN bolometric luminosity (log L_bol / erg s^-1 = 44.7 - 46.9) by using ALMA Band 3 observations of the CO(3-2) transition (∼1″ angular resolution). […]

February 2021: Circosta, C., Mainieri, V., Lamperti, I., Padovani, P., Bischetti, M., et al (Astronomy and Astrophysics)

Radiation Hydrodynamics of Turbulent H II Regions in Molecular Clouds: A Physical Origin of LyC Leakage and the Associated Lyα Spectra

We examine Lyman continuum (LyC) leakage through H II regions regulated by turbulence and radiative feedback in a giant molecular cloud in the context of fully coupled radiation hydrodynamics (RHD). The physical relations of the LyC escape with H I covering fraction, kinematics, ionizing photon production efficiency, and emergent Lyα line profiles are studied using a series of RHD turbulence simulations performed with RAMSES-RT. The turbulence-regulated mechanism allows ionizing photons to leak out at early times before the onset of supernova feedback. […]

February 2021: Kakiichi, Koki, Gronke, Max (The Astrophysical Journal)

KiDS-1000 methodology: Modelling and inference for joint weak gravitational lensing and spectroscopic galaxy clustering analysis

We present the methodology for a joint cosmological analysis of weak gravitational lensing from the fourth data release of the ESO Kilo-Degree Survey (KiDS-1000) and galaxy clustering from the partially overlapping Baryon Oscillation Spectroscopic Survey (BOSS) and the 2-degree Field Lensing Survey (2dFLenS). Cross-correlations between BOSS and 2dFLenS galaxy positions and source galaxy ellipticities have been incorporated into the analysis, necessitating the development of a hybrid model of non-linear scales that blends perturbative and non-perturbative approaches, and an assessment of signal contributions by astrophysical effects. All weak lensing signals were measured consistently via Fourier-space statistics that are insensitive to the survey mask and display low levels of mode mixing. […]

February 2021: Joachimi, B., Lin, C. -A., Asgari, M., Tröster, T., Heymans, C., et al (Astronomy and Astrophysics)

The ExoMolOP database: Cross sections and k-tables for molecules of interest in high-temperature exoplanet atmospheres

Here we present a publicly available database of opacities for molecules of astrophysical interest named ExoMolOP that has been compiled for over 80 species, and is based on the latest line list data from the ExoMol, HITEMP, and MoLLIST databases. These data are generally suitable for characterising high-temperature exoplanet or cool stellar and substellar atmospheres, and have been computed at a variety of pressures and temperatures, with a few molecules included at room temperature only from the HITRAN database. The data are formatted in different ways for four different exoplanet atmosphere retrieval codes; ARCiS, TauREx, NEMESIS, and petitRADTRANS, and include both cross sections (at R = λ/Δλ = 15000) and k-tables (at R = λ/Δλ = 1000) for the 0.3-50 μm wavelength region. […]

February 2021: Chubb, Katy L., Rocchetto, Marco, Yurchenko, Sergei N., Min, Michiel, Waldmann, Ingo, et al (Astronomy and Astrophysics)

Detectability of Rocky-Vapour atmospheres on super-Earths with Ariel

Ariel will mark the dawn of a new era as the first large-scale survey characterising exoplanetary atmospheres with science objectives to address fundamental questions about planetary composition, evolution and formation. In this study, we explore the detectability of atmospheres vaporised from magma oceans on dry, rocky Super-Earths orbiting very close to their host stars. The detection of such atmospheres would provide a definitive piece of evidence for rocky planets but are challenging measurements with currently available instruments due to their small spectral signatures. […]

January 2021: Ito, Yuichi, Changeat, Quentin, Edwards, Billy, Al-Refaie, Ahmed, Tinetti, Giovanna, et al (Experimental Astronomy)

Hubble WFC3 Spectroscopy of the Habitable-zone Super-Earth LHS 1140 b

Atmospheric characterization of temperate, rocky planets is the holy grail of exoplanet studies. These worlds are at the limits of our capabilities with current instrumentation in transmission spectroscopy and challenge our state-of-the-art statistical techniques. Here we present the transmission spectrum of the temperate super-Earth LHS 1140b using the Hubble Space Telescope (HST). […]

January 2021: Edwards, Billy, Changeat, Quentin, Mori, Mayuko, Anisman, Lara O., Morvan, Mario, et al (The Astronomical Journal)

Quenching and morphological evolution due to circumgalactic gas expulsion in a simulated galaxy with a controlled assembly history

We examine the influence of dark matter halo assembly on the evolution of a simulated ∼L^⋆ galaxy. Starting from a zoom-in simulation of a star-forming galaxy evolved with the EAGLE galaxy formation model, we use the genetic modification technique to create a pair of complementary assembly histories: one in which the halo assembles later than in the unmodified case, and one in which it assembles earlier. Delayed assembly leads to the galaxy exhibiting a greater present-day star formation rate than its unmodified counterpart, while in the accelerated case the galaxy quenches at z ≃ 1, and becomes spheroidal. […]

January 2021: Davies, Jonathan J., Crain, Robert A., Pontzen, Andrew (Monthly Notices of the Royal Astronomical Society)

How to build a catalogue of linearly evolving cosmic voids

Cosmic voids provide a powerful probe of the origin and evolution of structures in the Universe because their dynamics can remain near-linear to the present day. As a result, they have the potential to connect large-scale structure at late times to early Universe physics. Existing 'watershed'-based algorithms, however, define voids in terms of their morphological properties at low redshift. […]

January 2021: Stopyra, Stephen, Peiris, Hiranya V., Pontzen, Andrew (Monthly Notices of the Royal Astronomical Society)

The Hubble WFC3 Emission Spectrum of the Extremely Hot Jupiter KELT-9b

Recent studies of ultra-hot Jupiters suggested that their atmospheres could have thermal inversions due to the presence of optical absorbers such as titanium oxide (TiO), vanadium oxide (VO), iron hydride (FeH), and other metal hydride/oxides. However, it is expected that these molecules would thermally dissociate at extremely high temperatures, thus leading to featureless spectra in the infrared. KELT-9 b, the hottest exoplanet discovered so far, is thought to belong to this regime and host an atmosphere dominated by neutral hydrogen from dissociation and atomic/ionic species. […]

January 2021: Changeat, Quentin, Edwards, Billy (The Astrophysical Journal)

Machine Learning for Searching the Dark Energy Survey for Trans-Neptunian Objects

In this paper we investigate how implementing machine learning could improve the efficiency of the search for Trans-Neptunian Objects (TNOs) within Dark Energy Survey (DES) data when used alongside orbit fitting. The discovery of multiple TNOs that appear to show a similarity in their orbital parameters has led to the suggestion that one or more undetected planets, an as yet undiscovered "Planet 9", may be present in the outer solar system. DES is well placed to detect such a planet and has already been used to discover many other TNOs. […]

January 2021: Henghes, B., Lahav, O., Gerdes, D. W., Lin, H. W., Morgan, R., et al (Publications of the Astronomical Society of the Pacific)

Water ice deposition and growth in molecular clouds

In interstellar clouds, the deposition of water ice on to grains only occurs at visual extinctions above some threshold value (A_th). At extinctions greater than A_th, there is a (near-linear) correlation between the inferred column density of the water ice and A_V. For individual cloud complexes such as Taurus, Serpens, and ρ-Ophiuchi, A_th and the gradients of the correlation are very similar along all lines of sight. […]

January 2021: Rawlings, Jonathan M. C., Williams, D. A. (Monthly Notices of the Royal Astronomical Society)

Centrally concentrated molecular gas driving galactic-scale ionized gas outflows in star-forming galaxies

We perform a joint analysis of high spatial resolution molecular gas and star-formation rate (SFR) maps in main-sequence star-forming galaxies experiencing galactic-scale outflows of ionized gas. Our aim is to understand the mechanism that determines which galaxies are able to launch these intense winds. We observed CO(1→0) at 1-arcsec resolution with ALMA in 16 edge-on galaxies, which also have 2-arcsec spatial-resolution optical integral field observations from the SAMI Galaxy Survey. […]

January 2021: Hogarth, L. M., Saintonge, A., Cortese, L., Davis, T. A., Croom, S. M., et al (Monthly Notices of the Royal Astronomical Society)

Double-peaked Lyman α emission at z = 6.803: a reionization-era galaxy self-ionizing its local H II bubble

We report the discovery of a double-peaked Lyman α profile in a galaxy at z = 6.803, A370p_z1, in the parallel Frontier Field of Abell 370. The velocity separation between the blue and red peaks of the Lyman α profile ( $\Delta v=101_{-19}^{+38} (\pm 48)\, \rm km\, \rm s^{-1}$ ) suggests an extremely high escape fraction of ionizing photons $\gt 59(51){{\ \rm per\ cent}} (2\sigma)$ . The spectral energy distribution indicates a young (50 Myr), star-forming ( $12\pm 6 \, \rm {M}_\odot \rm {yr}^{-1}$ ) galaxy with an IRAC excess implying strong [O III] + H β emission. […]

January 2021: Meyer, Romain A., Laporte, Nicolas, Ellis, Richard S., Verhamme, Anne, Garel, Thibault (Monthly Notices of the Royal Astronomical Society)

On the Compatibility of Ground-based and Space-based Data: WASP-96 b, an Example

The study of exoplanetary atmospheres relies on detecting minute changes in the transit depth at different wavelengths. To date, a number of ground- and space-based instruments have been used to obtain transmission spectra of exoplanets in different spectral bands. One common practice is to combine observations from different instruments in order to achieve a broader wavelength coverage. […]

January 2021: Yip, Kai Hou, Changeat, Quentin, Edwards, Billy, Morvan, Mario, Chubb, Katy L., et al (The Astronomical Journal)

Sum of the masses of the Milky Way and M31: A likelihood-free inference approach

We use density estimation likelihood-free inference, Λ cold dark matter simulations of ∼2 M galaxy pairs, and data from Gaia and the Hubble Space Telescope to infer the sum of the masses of the Milky Way and Andromeda (M31) galaxies, the two main components of the local group. This method overcomes most of the approximations of the traditional timing argument, makes the writing of a theoretical likelihood unnecessary, and allows the nonlinear modeling of observational errors that take into account correlations in the data and non-Gaussian distributions. We obtain an M₂₀₀ mass estimate M_{MW +M 31}=4. […]

January 2021: Lemos, Pablo, Jeffrey, Niall, Whiteway, Lorne, Lahav, Ofer, Libeskind, Noam, et al (Physical Review D)