UCL Astrophysics Group


Latest Group Publications

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

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)

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)

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)

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)

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)

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 6 485 distinct energy levels. []

September 2021: Bowesman, Charles A., Shuai, Meiyin, Yurchenko, Sergei N., Tennyson, Jonathan (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)

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)

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. []

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

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)

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)

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)

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 Ng≈(m /Mp)2. []

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

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 broadband light curves are constructed. []

September 2021: Yu, B. P. Brian, Owen, Ellis R., Pan, Kuo-Chuan, Wu, Kinwah, Ferreras, Ignacio (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 (91,9-81,8), OCS (25-24), and CH3OH (21,1-20,2) toward a smaller subset of positions. []

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

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 (LX), 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 LX/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)

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)

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; comsmic 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. []

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

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 (AV), the steepness of the wavelength dependence (δ), and the bump strength (Eb). 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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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))

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)

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)

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)

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 Dn(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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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 σz ∼ 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)

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)

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)

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 Lbol / 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)

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)

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)

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)

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)

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)

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)

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)

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 (Ath). At extinctions greater than Ath, there is a (near-linear) correlation between the inferred column density of the water ice and AV. For individual cloud complexes such as Taurus, Serpens, and ρ-Ophiuchi, Ath 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)

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 MMW +M 31=4. []

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

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)

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)

MAGRITTE, a modern software library for 3D radiative transfer - II. Adaptive ray-tracing, mesh construction, and reduction

Radiative transfer is a notoriously difficult and computationally demanding problem. Yet, it is an indispensable ingredient in nearly all astrophysical and cosmological simulations. Choosing an appropriate discretization scheme is a crucial part of the simulation, since it not only determines the direct memory cost of the model but also largely determines the computational cost and the achievable accuracy. []

December 2020: De Ceuster, Frederik, Bolte, Jan, Homan, Ward, Maes, Silke, Malfait, Jolien, et al (Monthly Notices of the Royal Astronomical Society)

Exploiting Network Topology for Accelerated Bayesian Inference of Grain Surface Reaction Networks

In the study of grain-surface chemistry in the interstellar medium, there exists much uncertainty regarding the reaction mechanisms with few constraints on the abundances of grain-surface molecules. Bayesian inference can be performed to determine the likely reaction rates. In this work, we consider methods for reducing the computational expense of performing Bayesian inference on a reaction network by looking at the geometry of the network. []

December 2020: Heyl, Johannes, Viti, Serena, Holdship, Jonathan, Feeney, Stephen M. (The Astrophysical Journal)

First L band detection of hot exozodiacal dust with VLTI/MATISSE

For the first time, we observed the emission of hot exozodiacal dust in L band. We used the new instrument MATISSE at the Very Large Telescope Interferometer to detect the hot dust around κ Tuc with a significance of 3σ to 6σ at wavelengths between 3.37 and $3.85\, {\mu {\rm m}}$ and a dust-to-star flux ratio of 5 to $7{{{\ \rm per\ cent}}}$ . We modelled the spectral energy distribution based on the new L band data alone and in combination with H band data published previously. []

December 2020: Kirchschlager, Florian, Ertel, Steve, Wolf, Sebastian, Matter, Alexis, Krivov, Alexander V. (Monthly Notices of the Royal Astronomical Society)

Models of distorted and evolving dark matter haloes

We investigate the ability of basis function expansions to reproduce the evolution of a Milky Way-like dark matter halo, extracted from a cosmological zoom-in simulation. For each snapshot, the density of the halo is reduced to a basis function expansion, with interpolation used to recreate the evolution between snapshots. The angular variation of the halo density is described by spherical harmonics, and the radial variation either by biorthonormal basis functions adapted to handle truncated haloes or by splines. []

December 2020: Sanders, Jason L., Lilley, Edward J., Vasiliev, Eugene, Evans, N. Wyn, Erkal, Denis (Monthly Notices of the Royal Astronomical Society)

KELT-11 b: Abundances of Water and Constraints on Carbon-bearing Molecules from the Hubble Transmission Spectrum

In the past decade, the analysis of exoplanet atmospheric spectra has revealed the presence of water vapor in almost all the planets observed, with the exception of a fraction of overcast planets. Indeed, water vapor presents a large absorption signature in the wavelength coverage of the Hubble Space Telescope's (HST) Wide Field Camera 3 (WFC3), which is the main space-based observatory for atmospheric studies of exoplanets, making its detection very robust. However, while carbon-bearing species such as methane, carbon monoxide, and carbon dioxide are also predicted from current chemical models, their direct detection and abundance characterization has remained a challenge. []

December 2020: Changeat, Q., Edwards, B., Al-Refaie, A. F., Morvan, M., Tsiaras, A., et al (The Astronomical Journal)

Near-Gaussian distributions for modelling discrete stellar velocity data with heteroskedastic uncertainties

The velocity distributions of stellar tracers in general exhibit weak non-Gaussianity encoding information on the orbital composition of a galaxy and the underlying potential. The standard solution for measuring non-Gaussianity involves constructing a series expansion (e.g. the Gauss-Hermite series) that can produce regions of negative probability density. []

December 2020: Sanders, Jason L., Evans, N. Wyn (Monthly Notices of the Royal Astronomical Society)

The 2020 release of the ExoMol database: Molecular line lists for exoplanet and other hot atmospheres

The ExoMol database (www.exomol.com) provides molecular data for spectroscopic studies of hot atmospheres. While the data are intended for studies of exoplanets and other astronomical bodies, the dataset is widely applicable. The basic form of the database is extensive line lists; these are supplemented with partition functions, state lifetimes, cooling functions, Landé g-factors, temperature-dependent cross sections, opacities, pressure broadening parameters, k-coefficients and dipoles. []

November 2020: Tennyson, Jonathan, Yurchenko, Sergei N., Al-Refaie, Ahmed F., Clark, Victoria H. J., Chubb, Katy L., et al (Journal of Quantitative Spectroscopy and Radiative Transfer)

Analysing the Epoch of Reionization with three-point correlation functions and machine learning techniques

Three-point and high-order clustering statistics of the high-redshift 21 cm signal contain valuable information about the Epoch of Reionization (EoR). We present 3PCF-FAST, an optimized code for estimating the three-point correlation function (3PCF) of 3D pixelized data such as the outputs from numerical and seminumerical simulations. After testing 3PCF-FAST on data with known analytical 3PCF, we use machine learning techniques to recover the mean bubble size and global ionization fraction from correlations in the outputs of the publicly available 21CMFAST code. []

November 2020: Jennings, W. D., Watkinson, C. A., Abdalla, F. B. (Monthly Notices of the Royal Astronomical Society)

WASP-117 b: An Eccentric Hot Saturn as a Future Complex Chemistry Laboratory

We present spectral analysis of the transiting Saturn-mass planet WASP-117 b, observed with the G141 grism of the Hubble Space Telescope's (HST) Wide Field Camera 3. We reduce and fit the extracted spectrum from the raw transmission data using the open-source software Iraclis before performing a fully Bayesian retrieval using the publicly available analysis suite TauREx 3.0. We detect water vapor alongside a layer of fully opaque cloud, retrieving a terminator temperature of ${T}_{\mathrm{term}}={833}_{-156}^{+260}$ K. []

November 2020: Anisman, Lara O., Edwards, Billy, Changeat, Quentin, Venot, Olivia, Al-Refaie, Ahmed F., et al (The Astronomical Journal)

Experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun

For most of their existence, stars are fuelled by the fusion of hydrogen into helium. Fusion proceeds via two processes that are well understood theoretically: the proton-proton (pp) chain and the carbon-nitrogen-oxygen (CNO) cycle1,2. Neutrinos that are emitted along such fusion processes in the solar core are the only direct probe of the deep interior of the Sun. []

November 2020: Borexino Collaboration, Agostini, M., Altenmüller, K., Appel, S., Atroshchenko, V., Bagdasarian, Z., et al (Nature)

Unveiling cloudy exoplanets: the influence of cloud model choices on retrieval solutions

In recent years, it has become clear that a substantial fraction of transiting exoplanets have some form of aerosol present in their atmospheres. Transit spectroscopy - mostly of hot Jupiters, but also of some smaller planets - has provided evidence for this, in the form of steep downward slopes from blue to red in the optical part of the spectrum, and muted gas absorption features throughout. Retrieval studies seeking to constrain the composition of exoplanet atmospheres must therefore account for the presence of aerosols. []

October 2020: Barstow, Joanna K. (Monthly Notices of the Royal Astronomical Society)

Integrating Light Curve and Atmospheric Modeling of Transiting Exoplanets

Spectral retrieval techniques are currently our best tool to interpret the observed exoplanet atmospheric data. Said techniques retrieve the optimal atmospheric components and parameters by identifying the best fit to an observed transmission/emission spectrum. Over the past decade, our understanding of remote worlds in our galaxy has flourished thanks to the use of increasingly sophisticated spectral retrieval techniques and the collective effort of the community working on exoplanet atmospheric models. []

October 2020: Yip, K. H., Tsiaras, A., Waldmann, I. P., Tinetti, G. (The Astronomical Journal)

The Mean Absorption-line Spectra of a Selection of Luminous z ∼ 6 Lyman Break Galaxies

We examine the absorption-line spectra of a sample of 31 luminous ( ${M}_{\mathrm{UV}}\simeq -23$ ) Lyman break galaxies at redshift z ≃ 6 using data taken with the FOCAS and OSIRIS spectrographs on the Subaru and GTC telescopes. For two of these sources we present longer exposure data taken at higher spectral resolutions from ESO's X-shooter spectrograph. Using these data, we demonstrate the practicality of stacking our lower-resolution data to measure the depth of various interstellar and stellar absorption lines to probe the covering fraction of low-ionization gas and the gas phase and stellar metallicities near the end of the era of cosmic reionization. []

October 2020: Harikane, Yuichi, Laporte, Nicolas, Ellis, Richard S., Matsuoka, Yoshiki (The Astrophysical Journal)

A chemical study of carbon fractionation in external galaxies

In the interstellar medium carbon exists in the form of two stable isotopes 12C and 13C and their ratio is a good indicator of nucleosynthesis in galaxies. However, chemical fractionation can potentially significantly alter this ratio and in fact observations of carbon fractionation within the same galaxy has been found to vary from species to species. In this paper, we theoretically investigate the carbon fractionation for selected abundant carbon-bearing species in order to determine the conditions that may lead to a spread of the 12C/13C ratio in external galaxies. []

October 2020: Viti, Serena, Fontani, Francesco, Jiménez-Serra, Izaskun (Monthly Notices of the Royal Astronomical Society)

High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare

Context. We present a ~130 ks observation of the prototypical wind-accreting, high-mass X-ray binary Vela X-1 collected with XMM-Newton at orbital phases between 0.12 and 0.28. A strong flare took place during the observation that allows us to investigate the reaction of the clumpy stellar wind to the increased X-ray irradiation. []

September 2020: Lomaeva, M., Grinberg, V., Guainazzi, M., Hell, N., Bianchi, S., et al (Astronomy and Astrophysics)

Neutrino self-interactions and double beta decay

Neutrino self-interactions (ν SI ) beyond the Standard Model are an attractive possibility to soften cosmological constraints on neutrino properties and also to explain the tension in late and early time measurements of the Hubble expansion rate. The required strength of ν SI to explain the 4 σ Hubble tension is in terms of a pointlike effective four-fermion coupling that can be as high as 109GF, where GF is the Fermi constant. In this work, we show that such strong ν SI can cause significant effects in two-neutrino double beta decay, leading to an observable enhancement of decay rates and to spectrum distortions. []

September 2020: Deppisch, Frank F., Graf, Lukas, Rodejohann, Werner, Xu, Xun-Jie (Physical Review D)

ExoMol line lists - XL. Rovibrational molecular line list for the hydronium ion (H3O+)

A new line list for hydronium (H316O+) is computed. The line list is based on a new ab initio dipole moment surface (CCSD(T)/aug-cc-pVQZ) and a new empirical potential energy surface (PES). The empirical PES of H3O+ was obtained by refining an ab initio surface through a global fit to the experimentally determined rovibrational energies collected from the literature covering the ground, $\nu _1^{\pm }$ , $\nu _2^{\pm }$ , $2\nu _2^{\pm }$ , $\nu _3^{\pm }$ , and $\nu _4^{\pm }$ vibrational states. []

September 2020: Yurchenko, S. N., Tennyson, Jonathan, Miller, Steve, Melnikov, V. V., O'Donoghue, J., et al (Monthly Notices of the Royal Astronomical Society)

Interpreting the Spitzer/IRAC colours of 7 ≤ z ≤ 9 galaxies: distinguishing between line emission and starlight using ALMA

Prior to the launch of JWST, Spitzer/IRAC photometry offers the only means of studying the rest-frame optical properties of z >7 galaxies. Many such high-redshift galaxies display a red [3.6]-[4.5] micron colour, often referred to as the 'IRAC excess', which has conventionally been interpreted as arising from intense [O III]+H β emission within the [4.5] micron bandpass. An appealing aspect of this interpretation is similarly intense line emission seen in star-forming galaxies at lower redshift as well as the redshift-dependent behaviour of the IRAC colours beyond z ∼ 7 modelled as the various nebular lines move through the two bandpasses. []

September 2020: Roberts-Borsani, G. W., Ellis, R. S., Laporte, N. (Monthly Notices of the Royal Astronomical Society)

The two body problem in the presence of dark energy and modified gravity: application to the Local Group

We explore mass estimation of the Local Group via the use of the simple, dynamical `timing argument' in the context of a variety of theories of dark energy and modified gravity: a cosmological constant, a perfect fluid with constant equation of state w, quintessence (minimally coupled scalar field), MOND, and symmetrons (coupled scalar field). We explore generic coupled scalar field theories, with the symmetron model as an explicit example. We find that theories which attempt to eliminate dark matter by fitting rotation curves produce mass estimates in the timing argument which are not compatible with the luminous mass of the galaxies alone. []

September 2020: McLeod, M., Lahav, O. (Journal of Cosmology and Astroparticle Physics)

EDGE: from quiescent to gas-rich to star-forming low-mass dwarf galaxies

We study how star formation is regulated in low-mass field dwarf galaxies ( $10^5 \le M_{\star } \le 10^6 \, \mbox{M}_\mathrm{\odot }$ ), using cosmological high-resolution ( $3 \, \mathrm{pc}$ ) hydrodynamical simulations. Cosmic reionization quenches star formation in all our simulated dwarfs, but three galaxies with final dynamical masses of $3 \times 10^{9} \, \mbox{M}_\mathrm{\odot }$ are subsequently able to replenish their interstellar medium by slowly accreting gas. Two of these galaxies reignite and sustain star formation until the present day at an average rate of $10^{-5} \, \mbox{M}_\mathrm{\odot } \, \text{yr}^{-1}$ , highly reminiscent of observed low-mass star-forming dwarf irregulars such as Leo T. []

September 2020: Rey, Martin P., Pontzen, Andrew, Agertz, Oscar, Orkney, Matthew D. A., Read, Justin I., et al (Monthly Notices of the Royal Astronomical Society)

ARES. II. Characterizing the Hot Jupiters WASP-127 b, WASP-79 b, and WASP-62b with the Hubble Space Telescope

This paper presents the atmospheric characterization of three large, gaseous planets: WASP-127 b, WASP-79 b, and WASP-62 b. We analyzed spectroscopic data obtained with the G141 grism (1.088-1.68 μm) of the Wide Field Camera 3 on board the Hubble Space Telescope using the Iraclis pipeline and the TauREx3 retrieval code, both of which are publicly available. For WASP-127 b, which is the least dense planet discovered so far and is located in the short-period Neptune desert, our retrieval results found strong water absorption corresponding to an abundance of log(H2O) = -2.71 ${}_{-1.05}^{+0.78}$ and absorption compatible with an iron hydride abundance of log(FeH) = $-{5.25}_{-1.10}^{+0.88}$ , with an extended cloudy atmosphere. []

September 2020: Skaf, Nour, Bieger, Michelle Fabienne, Edwards, Billy, Changeat, Quentin, Morvan, Mario, et al (The Astronomical Journal)

ExoMol line lists - XXXIX. Ro-vibrational molecular line list for CO2

A new hot line list for the main isotopologue of CO212C16O2 is presented. The line list consists of almost 2.5 billion transitions between 3.5 million rotation-vibration states of CO2 in its ground electronic state, covering the wavenumber range 0-20 000 cm-1 (λ > 0.5 µm) with the upper and lower energy thresholds of 36 000 cm-1 and 16 000 cm-1, respectively. The ro-vibrational energies and wavefunctions are computed variationally using the accurate empirical potential energy surface Ames-2. []

August 2020: Yurchenko, S. N., Mellor, Thomas M., Freedman, Richard S., Tennyson, J. (Monthly Notices of the Royal Astronomical Society)

When do cosmic peaks, filaments, or walls merge? A theory of critical events in a multiscale landscape

The merging rate of cosmic structures is computed, relying on the ansatz that they can be predicted in the initial linear density field from the coalescence of critical points with increasing smoothing scale, used here as a proxy for cosmic time. Beyond the mergers of peaks with saddle points (a proxy for halo mergers), we consider the coalescence and nucleation of all sets of critical points, including wall-saddle to filament-saddle and wall-saddle to minima (a proxy for filament and void mergers, respectively), as they impact the geometry of galactic infall, and in particular filament disconnection. Analytical predictions of the one-point statistics are validated against multiscale measurements in 2D and 3D realizations of Gaussian random fields (the corresponding code being available upon request) and compared qualitatively to cosmological N-body simulations at early times (z ≥ 10) and large scales (${\ge} {5}\, \mathrm{Mpc}\, h^{-1}$). []

August 2020: Cadiou, C., Pichon, C., Codis, S., Musso, M., Pogosyan, D., et al (Monthly Notices of the Royal Astronomical Society)

X-ray properties of He II λ 1640 emitting galaxies in VANDELS

We explore X-ray emission from a sample of 18 He II λ1640 emitting star-forming galaxies at z ∼ 2.3-3.6 from the VANDELS survey in the Chandra Deep Field South, to set constraints on the role of X-ray sources in powering the He II emission. We find that 4 He II emitters have tentative detections with S/N ∼ 2 and have X-ray luminosities, LX = 1.5-4.9 × 1041 erg s-1. The stacked luminosity of all 18 He II emitters is 2.6 × 1041 erg s-1, and that of a subset of 13 narrow He II emitters (FHWM(He II) < 1000 km s-1) is 3.1 × 1041 erg s-1. []

August 2020: Saxena, A., Pentericci, L., Schaerer, D., Schneider, R., Amorin, R., et al (Monthly Notices of the Royal Astronomical Society)

Quantifying Suspiciousness within correlated data sets

We propose a principled Bayesian method for quantifying tension between correlated data sets with wide uninformative parameter priors. This is achieved by extending the Suspiciousness statistic, which is insensitive to priors. Our method uses global summary statistics, and as such it can be used as a diagnostic for internal consistency. []

August 2020: Lemos, Pablo, Köhlinger, Fabian, Handley, Will, Joachimi, Benjamin, Whiteway, Lorne, et al (Monthly Notices of the Royal Astronomical Society)

ALMA observations of CS in NGC 1068: chemistry and excitation

We present results from Atacama Large Millimeter/submillimeter Array (ALMA) observations of CS from the nearby galaxy NGC 1068 (~14 Mpc). This Seyfert 2 barred galaxy possesses a circumnuclear disc (CND, r ~ 200 pc) and a starburst ring (SB ring, r ~ 1.3 kpc). These high-resolution maps (~0.5 arcsec, ~35 pc) allow us to analyse specific sub-regions in the galaxy and investigate differences in line intensity ratios and physical conditions, particularly those between the CND and SB ring. []

August 2020: Scourfield, M., Viti, S., García-Burillo, S., Saintonge, A., Combes, F., et al (Monthly Notices of the Royal Astronomical Society)

The dust never settles: collisional production of gas and dust in evolved planetary systems

Multi-epoch infrared photometry from Spitzer is used to monitor circumstellar discs at white dwarfs, which are consistent with disrupted minor planets whose debris is accreted and chemically reflected by their host stars. Widespread infrared variability is found across the population of 37 stars with two or more epochs. Larger flux changes occur on longer time-scales, reaching several tens of per cent over baselines of a few years. []

August 2020: Swan, Andrew, Farihi, Jay, Wilson, Thomas G., Parsons, Steven G. (Monthly Notices of the Royal Astronomical Society)

Mesoscopic interference for metric and curvature & gravitational wave detection

A compact detector for space-time metric and curvature is highly desirable. Here we show that quantum spatial superpositions of mesoscopic objects could be exploited to create such a detector. We propose a specific form for such a detector and analyse how asymmetries in its design allow it to directly couple to the curvature. []

August 2020: Marshman, Ryan J., Mazumdar, Anupam, Morley, Gavin W., Barker, Peter F., Hoekstra, Steven, et al (New Journal of Physics)

TauREx3 PhaseCurve: A 1.5D Model for Phase-curve Description

In recent years, retrieval analysis of exoplanet atmospheres have been very successful, providing deep insights on the composition and the temperature structure of these worlds via transit and eclipse methods. Analysis of spectral phase-curve observations, which in theory provide even more information, are still limited to a few planets. In the next decade, new facilities such as NASA-James Webb Space Telescope and ESA-Ariel will revolutionize the field of exoplanet atmospheres and we expect that a significant time will be spent on spectral phase-curve observations. []

August 2020: Changeat, Q., Al-Refaie, A. (The Astrophysical Journal)

The impact of spectroscopic incompleteness in direct calibration of redshift distributions for weak lensing surveys

Obtaining accurate distributions of galaxy redshifts is a critical aspect of weak lensing cosmology experiments. One of the methods used to estimate and validate redshift distributions is to apply weights to a spectroscopic sample, so that their weighted photometry distribution matches the target sample. In this work, we estimate the selection bias in redshift that is introduced in this procedure. []

August 2020: Hartley, W. G., Chang, C., Samani, S., Carnero Rosell, A., Davis, T. M., et al (Monthly Notices of the Royal Astronomical Society)

JINGLE - IV. Dust, H I gas, and metal scaling laws in the local Universe

Scaling laws of dust, H I gas, and metal mass with stellar mass, specific star formation rate, and metallicity are crucial to our understanding of the build-up of galaxies through their enrichment with metals and dust. In this work, we analyse how the dust and metal content varies with specific gas mass (MH I/M) across a diverse sample of 423 nearby galaxies. The observed trends are interpreted with a set of Dust and Element evolUtion modelS (DEUS) - including stellar dust production, grain growth, and dust destruction - within a Bayesian framework to enable a rigorous search of the multidimensional parameter space. []

August 2020: De Looze, I., Lamperti, I., Saintonge, A., Relaño, M., Smith, M. W. L., et al (Monthly Notices of the Royal Astronomical Society)

Alfnoor: A Retrieval Simulation of the Ariel Target List

In this work, we present Alfnoor, a dedicated tool optimized for population studies of exoplanet atmospheres. Alfnoor combines the latest version of the retrieval algorithm, TauREx 3, with the instrument noise simulator ArielRad and enables the simultaneous retrieval analysis of a large sample of exo-atmospheres. We applied this tool to the Ariel list of planetary candidates and focus on hydrogen dominated, cloudy atmospheres observed in transit with the Tier-2 mode (medium Ariel resolution). []

August 2020: Changeat, Q., Al-Refaie, A., Mugnai, L. V., Edwards, B., Waldmann, I. P., et al (The Astronomical Journal)

Bayesian methods for fitting Baryon Acoustic Oscillations in the Lyman-α forest

We study and compare fitting methods for the Lyman-α (Lyα) forest 3D correlation function. We use the nested sampler PolyChord and the community code picca to perform a Bayesian analysis which we compare with previous frequentist analyses. By studying synthetic correlation functions, we find that the frequentist profile likelihood produces results in good agreement with a full Bayesian analysis. []

July 2020: Cuceu, Andrei, Font-Ribera, Andreu, Joachimi, Benjamin (Journal of Cosmology and Astroparticle Physics)

Thirty years of H3+ astronomy

This review covers the work of the three decades since the first spectroscopic identification of the H3+ molecular ion outside of the laboratory in 1988, in the auroral atmosphere of the giant planet Jupiter. These decades have seen the astronomy related to this simple molecular ion expand to such an extent that a summary and evaluation of some 450 refereed articles is provided in the review. This enormous body of work has revealed surprises and illuminated the extensive role played by H3+ in astrophysical environments in our Solar System and beyond. []

July 2020: Miller, Steve, Tennyson, Jonathan, Geballe, Thomas R., Stallard, Tom (Reviews of Modern Physics)

Trapped Particle Motion in Magnetodisk Fields

The spatial and temporal characterization of trapped charged particle trajectories in magnetospheres has been extensively studied in dipole magnetic field structures. Such studies have allowed the calculation of spatial quantities, such as equatorial loss cone size as a function of radial distance, the location of the mirror points along particular field lines (L-shells) as a function of the particle's equatorial pitch angle, and temporal quantities such as the bounce period and drift period as a function of the radial distance and the particle's pitch angle at the equator. In this study, we present analogous calculations for the disk-like field structure associated with the giant rotation-dominated magnetospheres of Jupiter and Saturn as described by the University College London/Achilleos-Guio-Arridge (UCL/AGA) magnetodisk model. []

July 2020: Guio, P., Staniland, N. R., Achilleos, N., Arridge, C. S. (Journal of Geophysical Research (Space Physics))

ARES I: WASP-76 b, A Tale of Two HST Spectra

We analyze the transmission and emission spectra of the ultra-hot Jupiter WASP-76 b, observed with the G141 grism of the Hubble Space Telescope's (HST) Wide Field Camera 3 (WFC3). We reduce and fit the raw data for each observation using the open-source software Iraclis before performing a fully Bayesian retrieval using the publicly available analysis suite TauREx 3. Previous studies of the WFC3 transmission spectra of WASP-76 b found hints of titanium oxide (TiO) and vanadium oxide (VO) or non-gray clouds. []

July 2020: Edwards, Billy, Changeat, Quentin, Baeyens, Robin, Tsiaras, Angelos, Al-Refaie, Ahmed, et al (The Astronomical Journal)

The impact of peculiar velocities on the estimation of the Hubble constant from gravitational wave standard sirens

In this work, we investigate the systematic uncertainties that arise from the calculation of the peculiar velocity when estimating the Hubble constant (H0) from gravitational wave standard sirens. We study the GW170817 event and the estimation of the peculiar velocity of its host galaxy, NGC 4993, when using Gaussian smoothing over nearby galaxies. NGC 4993 being a relatively nearby galaxy, at ∼40 Mpc away, is subject to a significant effect of peculiar velocities. []

June 2020: Nicolaou, Constantina, Lahav, Ofer, Lemos, Pablo, Hartley, William, Braden, Jonathan (Monthly Notices of the Royal Astronomical Society)

ExoMol line lists - XXXVIII. High-temperature molecular line list of silicon dioxide (SiO2)

Silicon dioxide (SiO2) is expected to occur in the atmospheres of hot rocky super-Earth exoplanets but a lack of spectroscopic data is hampering its possible detection. Here, we present the first, comprehensive molecular line list for SiO2. The line list, named OYT3, covers the wavenumber range 0 - 6000 cm-1 (wavelengths λ > 1.67 μm) and is suitable for temperatures up to T = 3000 K. []

June 2020: Owens, A., Conway, E. K., Tennyson, J., Yurchenko, S. N. (Monthly Notices of the Royal Astronomical Society)

Three Lyα Emitting Galaxies within a Quasar Proximity Zone at z ∼ 5.8

Quasar proximity zones at $z\gt 5.5$ correspond to overdense and overionized environments. Galaxies found inside proximity zones can therefore display features that would otherwise be masked by absorption in the intergalactic medium. We demonstrate the utility of this quasar-galaxy synergy by reporting the discovery of the first three "proximate Lyα emitters" (LAEs) within the proximity zone of quasar J0836+0054 at z = 5.795 (Aerith A, B, and C). []

June 2020: Bosman, Sarah E. I., Kakiichi, Koki, Meyer, Romain A., Gronke, Max, Laporte, Nicolas, et al (The Astrophysical Journal)

Impact of Planetary Mass Uncertainties on Exoplanet Atmospheric Retrievals

In current models used to interpret exoplanet atmospheric observations, the planetary mass is treated as a prior and is measured/estimated independently with external methods, such as radial velocity or transit timing variation techniques. This approach is necessary as available spectroscopic data do not have sufficient wavelength coverage and/or signal-to-noise to infer the planetary mass. We examine here whether the planetary mass can be directly retrieved from transit spectra as observed by future space observatories, which will provide higher quality spectra. []

June 2020: Changeat, Q., Keyte, L., Waldmann, I. P., Tinetti, G. (The Astrophysical Journal)

Self-scattering of non-spherical dust grains. The limitations of perfect compact spheres

Context. The understanding of (sub-)millimetre polarisation has made a leap forward since high-resolution imaging with the Atacama Large (sub-)Mm Array (ALMA) became available. Amongst other effects, self-scattering (i.e. []

June 2020: Kirchschlager, Florian, Bertrang, Gesa H. -M. (Astronomy and Astrophysics)

Large Population of ALMA Galaxies at z > 6 with Very High [O III] 88 μm to [C II] 158 μm Flux Ratios: Evidence of Extremely High Ionization Parameter or PDR Deficit?

We present our new Atacama Large Millimeter/Submillimeter Array (ALMA) observations targeting [O III]88 μm, [C II]158 μm, [N II]122 μm, and dust-continuum emission for three Lyman break galaxies at z = 6.0293-6.2037, identified in the Subaru/Hyper Suprime-Cam survey. We clearly detect [O III] and [C II] lines from all of the galaxies at 4.3-11.8σ levels, and identify multi-band dust-continuum emission in two of the three galaxies, allowing us to estimate infrared luminosities and dust temperatures simultaneously. In conjunction with previous ALMA observations for six galaxies at z > 6, we confirm that all the nine z = 6-9 galaxies have high [O III]/[C II] ratios of ${L}_{[{\rm{O}}{\rm{III}}]}/{L}_{[{\rm{C}}{\rm{II}}]}\sim 3\mbox{--}20$, ∼10 times higher than z ∼ 0 galaxies. []

June 2020: Harikane, Yuichi, Ouchi, Masami, Inoue, Akio K., Matsuoka, Yoshiki, Tamura, Yoichi, et al (The Astrophysical Journal)

Outstanding Challenges of Exoplanet Atmospheric Retrievals

Spectral retrieval has long been a powerful tool for interpreting planetary remote sensing observations. Flexible, parameterised, agnostic models are coupled with inversion algorithms in order to infer atmospheric properties directly from observations, with minimal reliance on physical assumptions. This approach, originally developed for application to Earth satellite data and subsequently observations of other Solar System planets, has been recently and successfully applied to transit, eclipse and phase curve spectra of transiting exoplanets. []

June 2020: Barstow, Joanna K., Heng, Kevin (Space Science Reviews)

The role of galaxies and AGN in reionizing the IGM - III. IGM-galaxy cross-correlations at z ∼ 6 from eight quasar fields with DEIMOS and MUSE

We present improved results of the measurement of the correlation between galaxies and the intergalactic medium transmission at the end of reionization. We have gathered a sample of 13 spectroscopically confirmed Lyman-break galaxies (LBGs) and 21 Lyman-α emitters (LAEs) at angular separations 20 arcsec ≲ θ ≲ 10 arcmin (∼0.1-4 pMpc at z ∼ 6) from the sightlines to eight background z ≳ 6 quasars. We report for the first time the detection of an excess of Lyman-α transmission spikes at ∼10-60 cMpc from LAEs (3.2σ) and LBGs (1.9σ). []

May 2020: Meyer, Romain A., Kakiichi, Koki, Bosman, Sarah E. I., Ellis, Richard S., Laporte, Nicolas, et al (Monthly Notices of the Royal Astronomical Society)

Observational constraints on the multiphase nature of outflows using large spectroscopic surveys at z ∼ 0

Mass outflow rates and loading factors are typically used to infer the quenching potential of galactic-scale outflows. However, these generally rely on observations of a single gas phase that can severely underestimate the total ejected gas mass. To address this, we use observations of high mass (≥1010 M), normal star-forming galaxies at z ∼ 0 from the MaNGA, xCOLD GASS, xGASS, and ALFALFA surveys and a stacking of Na D, Hα, CO(1-0), and H I 21 cm tracers with the aim of placing constraints on an average, total mass outflow rate, and loading factor. []

May 2020: Roberts-Borsani, G. W. (Monthly Notices of the Royal Astronomical Society)

COBRaS: The e-MERLIN 21 cm Legacy survey of Cygnus OB2

Context. The role of massive stars is central to an understanding of galactic ecology. It is important to establish the details of how massive stars provide radiative, chemical, and mechanical feedback in galaxies. []

May 2020: Morford, J. C., Fenech, D. M., Prinja, R. K., Blomme, R., Yates, J. A., et al (Astronomy and Astrophysics)

Disentangling Dust Components in SN 2010jl: The First 1400 Days

The luminous Type IIn SN 2010jl shows strong signs of interaction between the SN ejecta and dense circumstellar material. Dust may be present in the unshocked ejecta; the cool, dense shell (CDS) between the shocks in the interaction region; or in the circumstellar medium (CSM). We present and model new optical and infrared photometry and spectroscopy of SN 2010jl from 82 to 1367 days since explosion. []

May 2020: Bevan, A. M., Krafton, K., Wesson, R., Andrews, J. E., Montiel, E., et al (The Astrophysical Journal)

Distinguishing high-mass binary neutron stars from binary black holes with second- and third-generation gravitational wave observatories

While the gravitational-wave (GW) signal GW170817 was accompanied by a variety of electromagnetic (EM) counterparts, sufficiently high-mass binary neutron star (BNS) mergers are expected to be unable to power bright EM counterparts. The putative high-mass binary BNS merger GW190425, for which no confirmed EM counterpart has been identified, may be an example of such a system. Since current and future GW detectors are expected to detect many more BNS mergers, it is important to understand how well we will be able to distinguish high-mass BNSs and low-mass binary black holes (BBHs) solely from their GW signals. []

May 2020: Chen, An, Johnson-McDaniel, Nathan K., Dietrich, Tim, Dudi, Reetika (Physical Review D)

MARVEL Analysis of the Measured High-resolution Rovibronic Spectra of the Calcium Monohydroxide Radical (CaOH)

The calcium monohydroxide radical (CaOH) is an important astrophysical molecule relevant to cool stars and rocky exoplanets, among other astronomical environments. Here, we present a consistent set of highly accurate rovibronic (rotation-vibration-electronic) energy levels for the five lowest electronic states ( $\tilde{X}{}^{2}{{\rm{\Sigma }}}^{+}$ , $\tilde{A}{}^{2}{\rm{\Pi }}$ , $\tilde{B}{}^{2}{{\rm{\Sigma }}}^{+}$ , $\tilde{C}{}^{2}{\rm{\Delta }}$ , and $\tilde{D}{}^{2}{{\rm{\Sigma }}}^{+}$ ) of CaOH. A comprehensive analysis of the published spectroscopic literature on this system has allowed 1955 energy levels to be determined from 3204 rovibronic experimental transitions, all with unique quantum number labeling and measurement uncertainties. []

May 2020: Wang, Yixin, Owens, Alec, Tennyson, Jonathan, Yurchenko, Sergei N. (The Astrophysical Journal Supplement Series)

Locality and entanglement in table-top testing of the quantum nature of linearized gravity

This paper points out the importance of the assumption of locality of physical interactions, and the concomitant necessity of propagation of an entity (in this case, off-shell quanta—virtual gravitons) between two nonrelativistic test masses in unveiling the quantum nature of linearized gravity through a laboratory experiment. At the outset, we will argue that observing the quantum nature of a system is not limited to evidencing O (ℏ ) corrections to a classical theory: it instead hinges upon verifying tasks that a classical system cannot accomplish. We explain the background concepts needed from quantum field theory and quantum information theory to fully appreciate the previously proposed table-top experiments, namely forces arising through the exchange of virtual (off-shell) quanta, as well as local operations and classical communication (LOCC) and entanglement witnesses. []

May 2020: Marshman, Ryan J., Mazumdar, Anupam, Bose, Sougato (Physical Review A)

The high-temperature rotation-vibration spectrum and rotational clustering of silylene (SiH2)

A rotation-vibration line list for the electronic ground state (X∼1A1) of SiH2 is presented. The line list, named CATS, is suitable for temperatures up to 2000 K and covers the wavenumber range 0-10 000 cm-1 (wavelengths > 1.0 μm) for states with rotational excitation up to J = 52 . Over 310 million transitions between 593 804 energy levels have been computed variationally with a new empirically refined potential energy surface, determined by refining to 75 empirical term values with J ≤ 5 and a newly computed high-level ab initio dipole moment surface. []

May 2020: Clark, Victoria H. J., Owens, Alec, Tennyson, Jonathan, Yurchenko, Sergei N. (Journal of Quantitative Spectroscopy and Radiative Transfer)

Magnetopause Compressibility at Saturn with Internal Drivers

We use magnetopause crossings of the Cassini spacecraft to study the response of Saturn's magnetosphere to changes in external and internal drivers. We explain how solar wind pressure can be corrected to account for the local variability in internal plasma particle pressure. The physics-based method is applied to perform the most robust estimation of magnetopause compressibility at Saturn to date, using 7 years' worth of magnetometer data from the Cassini mission and accounting for variable internal drivers—particle pressure and azimuthal ring current. []

May 2020: Hardy, Flavien, Achilleos, Nicholas, Guio, Patrick (Geophysical Research Letters)

H2O2-induced Greenhouse Warming on Oxidized Early Mars

The existence of liquid water within an oxidized environment on early Mars has been inferred by the Mn-rich rocks found during recent explorations on Mars. The oxidized atmosphere implied by the Mn-rich rocks would basically be comprised of CO2 and H2O without any reduced greenhouse gases such as H2 and CH4. So far, however, it has been thought that early Mars could not have been warm enough to sustain water in liquid form without the presence of reduced greenhouse gases. []

April 2020: Ito, Yuichi, Hashimoto, George L., Takahashi, Yoshiyuki O., Ishiwatari, Masaki, Kuramoto, Kiyoshi (The Astrophysical Journal)

Target neutrino mass precision for determining the neutrino hierarchy

Recent works combining neutrino oscillation and cosmological data to determine the neutrino hierarchy found a range of odds in favor of the normal hierarchy. These results arise from differing approaches to incorporating prior knowledge about neutrinos. We develop a hierarchy-agnostic prior and show that the hierarchy cannot be conclusively determined with current data. []

April 2020: Mahony, Constance, Leistedt, Boris, Peiris, Hiranya V., Braden, Jonathan, Joachimi, Benjamin, et al (Physical Review D)

Reviving Horndeski theory using teleparallel gravity after GW170817

Horndeski gravity was highly constrained from the recent gravitational wave observations by the LIGO Collaboration down to |cg/c -1 |≳10-15. In this paper, we study the propagation of gravitational waves in a recently proposed model of Horndeski gravity in which its teleparallel gravity analog is formulated. As usually done in these analyses, we consider a flat cosmological background in which curvature is replaced by torsion as the expression of gravitation. []

April 2020: Bahamonde, Sebastian, Dialektopoulos, Konstantinos F., Gakis, Viktor, Said, Jackson Levi (Physical Review D)

Stellar mass as a galaxy cluster mass proxy: application to the Dark Energy Survey redMaPPer clusters

We introduce a galaxy cluster mass observable, μ, based on the stellar masses of cluster members, and we present results for the Dark Energy Survey (DES) Year 1 (Y1) observations. Stellar masses are computed using a Bayesian model averaging method, and are validated for DES data using simulations and COSMOS data. We show that μ works as a promising mass proxy by comparing our predictions to X-ray measurements. []

April 2020: Palmese, A., Annis, J., Burgad, J., Farahi, A., Soares-Santos, M., et al (Monthly Notices of the Royal Astronomical Society)

Silicate Grain Growth due to Ion Trapping in Oxygen-rich Supernova Remnants like Cassiopeia A

Core-collapse supernovae can condense large masses of dust post-explosion. However, sputtering and grain-grain collisions during the subsequent passage of the dust through the reverse shock can potentially destroy a significant fraction of the newly formed dust before it can reach the interstellar medium. Here we show that in oxygen-rich supernova remnants like Cassiopeia A, the penetration and trapping within silicate grains of the same impinging ions of oxygen, silicon, and magnesium that are responsible for grain surface sputtering can significantly reduce the net loss of grain material. []

April 2020: Kirchschlager, Florian, Barlow, M. J., Schmidt, Franziska D. (The Astrophysical Journal)

Dark Energy: is it 'just' Einstein's Cosmological Constant Λ?

The Cosmological Constant Λ, a concept introduced by Einstein in 1917, has been with us ever since in different variants and incarnations, including the broader concept of 'Dark Energy'. Current observations are consistent with a value of Λ corresponding to about present-epoch 70% of the critical density of the Universe. This is causing the speeding up (acceleration) of the expansion of the Universe. []

April 2020: Lahav, Ofer (Contemporary Physics)

Outflows in star-forming galaxies: Stacking analyses of resolved winds and the relation to their hosts' properties

Outflows form an integral component in regulating the gas cycling in and out of galaxies, although their impact on the galaxy hosts is still poorly understood. Here we present an analysis of 405 high mass (log M*/M ≥ 10), star-forming galaxies (excluding AGN) with low inclinations at z ∼ 0, using stacking techniques of the Na D λλ5889, 5895 Å neutral gas tracer in IFU observations from the MaNGA DR15 survey. We detect outflows in the central regions of 78/405 galaxies and determine their extent and power through the construction of stacked annuli. []

April 2020: Roberts-Borsani, G. W., Saintonge, A., Masters, K. L., Stark, D. V. (Monthly Notices of the Royal Astronomical Society)

Revealing and concealing entanglement with noninertial motion

Photon interference and bunching are widely studied quantum effects that have also been proposed for high-precision measurements. Here, we construct a theoretical description of photon interferometry on rotating platforms, specifically exploring the relation between noninertial motion, relativity, and quantum mechanics. On the basis of this, we then propose an experiment where photon entanglement can be revealed or concealed solely by controlling the rotational motion of an interferometer, thus providing a route towards studies at the boundary between quantum mechanics and relativity.

April 2020: Toroš, Marko, Restuccia, Sara, Gibson, Graham M., Cromb, Marion, Ulbricht, Hendrik, et al (Physical Review A)

ExoMol molecular line lists - XXXVII. Spectra of acetylene

A new ro-vibrational line list for the ground electronic state of the main isotopologue of acetylene, 12C2H2, is computed as part of the ExoMol project. The aCeTY line list covers the transition wavenumbers up to 10 000 cm-1 (λ > 1 μm), with lower and upper energy levels up to 12 000 and 22 000 cm-1 considered, respectively. The calculations are performed up to a maximum value for the vibrational angular momentum, Kmax = Lmax = 16, and maximum rotational angular momentum, J = 99. []

April 2020: Chubb, Katy L., Tennyson, Jonathan, Yurchenko, Sergei N. (Monthly Notices of the Royal Astronomical Society)

A comparison of exoplanet spectroscopic retrieval tools

Over the last several years, spectroscopic observations of transiting exoplanets have begun to uncover information about their atmospheres, including atmospheric composition and indications of the presence of clouds and hazes. Spectral retrieval is the leading technique for interpretation of transmission spectra and is employed by several teams using a variety of forward models and parameter estimation algorithms. However, different model suites have mostly been used in isolation and so it is unknown whether the results from each are comparable. []

April 2020: Barstow, Joanna K., Changeat, Quentin, Garland, Ryan, Line, Michael R., Rocchetto, Marco, et al (Monthly Notices of the Royal Astronomical Society)

Massive neutrinos and degeneracies in Lyman-alpha forest simulations

Using a suite of hydrodynamical simulations with cold dark matter, baryons, and neutrinos, we present a detailed study of the effect of massive neutrinos on the 1-D and 3-D flux power spectra of the Lyman-α (Lyα) forest. The presence of massive neutrinos in cosmology induces a scale- and time-dependent suppression of structure formation that is strongest on small scales. Measuring this suppression is a key method for inferring neutrino masses from cosmological data, and is one of the main goals of ongoing and future surveys like eBOSS, DES, LSST, Euclid or DESI . []

April 2020: Pedersen, Christian, Font-Ribera, Andreu, Kitching, Thomas D., McDonald, Patrick, Bird, Simeon, et al (Journal of Cosmology and Astroparticle Physics)

Deep learning dark matter map reconstructions from DES SV weak lensing data

We present the first reconstruction of dark matter maps from weak lensing observational data using deep learning. We train a convolution neural network with a U-Net-based architecture on over 3.6 × 105 simulated data realizations with non-Gaussian shape noise and with cosmological parameters varying over a broad prior distribution. We interpret our newly created dark energy survey science verification (DES SV) map as an approximation of the posterior mean P(κ|γ) of the convergence given observed shear. []

March 2020: Jeffrey, Niall, Lanusse, François, Lahav, Ofer, Starck, Jean-Luc (Monthly Notices of the Royal Astronomical Society)

Detrending Exoplanetary Transit Light Curves with Long Short-term Memory Networks

The precise derivation of transit depths from transit light curves is a key component for measuring exoplanet transit spectra, and henceforth for the study of exoplanet atmospheres. However, it is still deeply affected by various kinds of systematic errors and noise. In this paper we propose a new detrending method by reconstructing the stellar flux baseline during transit time. []

March 2020: Morvan, Mario, Nikolaou, Nikolaos, Tsiaras, Angelos, Waldmann, Ingo P. (The Astronomical Journal)

A hydrodynamical study of outflows in starburst galaxies with different driving mechanisms

Outflows from starburst galaxies can be driven by thermal pressure, radiation, and cosmic rays. We present an analytic phenomenological model that accounts for these contributions simultaneously to investigate their effects on the hydrodynamical properties of outflows. We assess the impact of energy injection, wind opacity, magnetic field strength, and the mass of the host galaxy on flow velocity, temperature, density, and pressure profiles. []

March 2020: Yu, B. P. Brian, Owen, Ellis R., Wu, Kinwah, Ferreras, Ignacio (Monthly Notices of the Royal Astronomical Society)

The CO(3-2)/CO(1-0) Luminosity Line Ratio in Nearby Star-forming Galaxies and Active Galactic Nuclei from xCOLD GASS, BASS, and SLUGS

We study the ${r}_{31}={L}_{\mathrm{CO}(3\mbox{--}2)}^{{\prime} }/{L}_{\mathrm{CO}(1\mbox{--}0)}^{{\prime} }$ luminosity line ratio in a sample of nearby (z < 0.05) galaxies: 25 star-forming galaxies (SFGs) from the xCOLD GASS survey, 36 hard X-ray-selected active galactic nucleus (AGN) host galaxies from the BAT AGN Spectroscopic Survey, and 37 infrared-luminous galaxies from the SCUBA Local Universe Galaxy Survey. We find a trend for r31 to increase with star formation efficiency (SFE). We model r31 using the UCL-PDR code and find that the gas density is the main parameter responsible for the variation of r31, while the interstellar radiation field and cosmic-ray ionization rate play only a minor role. []

February 2020: Lamperti, Isabella, Saintonge, Amélie, Koss, Michael, Viti, Serena, Wilson, Christine D., et al (The Astrophysical Journal)

MAGRITTE, a modern software library for 3D radiative transfer: I. Non-LTE atomic and molecular line modelling

Radiative transfer is a key component in almost all astrophysical and cosmological simulations. We present MAGRITTE: a modern open-source software library for 3D radiative transfer. It uses a deterministic ray-tracer and formal solver, I.e. []

February 2020: De Ceuster, Frederik, Homan, Ward, Yates, Jeremy, Decin, Leen, Boyle, Peter, et al (Monthly Notices of the Royal Astronomical Society)

Tracing shock type with chemical diagnostics. An application to L1157

Aims: The physical structure of a shock wave may take a form unique to its shock type, implying that the chemistry of each shock type is unique as well. We aim to investigate the different chemistries of J-type and C-type shocks in order to identify unique molecular tracers of both shock types. We apply these diagnostics to the protostellar outflow L1157 to establish whether the B2 clump could host shocks exhibiting type-specific behaviour. []

February 2020: James, T. A., Viti, S., Holdship, J., Jiménez-Serra, I. (Astronomy and Astrophysics)

ExoTETHyS: Tools for Exoplanetary Transits around host stars


February 2020: Morello, Giuseppe, Claret, Antonio, Martin-Lagarde, Marine, Cossou, Christophe, Tsiara, Angelos, et al (The Journal of Open Source Software)

The ExoTETHyS Package: Tools for Exoplanetary Transits around Host Stars

We present here the first release of the open-source python package ExoTETHyS (stable: https://zenodo.org/badge/latestdoi/169268509, development version: https://github.com/ucl-exoplanets/ExoTETHyS/), which aims to provide a stand-alone set of tools for modeling spectrophotometric observations of transiting exoplanets. In particular, we describe: (1) a new calculator of stellar limb-darkening coefficients that outperforms the existing software by one order of magnitude in terms of light-curve model accuracy, i.e., down to <10 parts per million, and (2) an exact transit light-curve generator based on the entire stellar intensity profile rather than limb-darkening coefficients. New tools will be added in later releases to model various effects in exoplanetary transits and eclipsing binaries. []

February 2020: Morello, G., Claret, A., Martin-Lagarde, M., Cossou, C., Tsiaras, A., et al (The Astronomical Journal)

Beyond two-point statistics: using the minimum spanning tree as a tool for cosmology

Cosmological studies of large-scale structure have relied on two-point statistics, not fully exploiting the rich structure of the cosmic web. In this paper we show how to capture some of this cosmic web information by using the minimum spanning tree (MST), for the first time using it to estimate cosmological parameters in simulations. Discrete tracers of dark matter such as galaxies, N-body particles or haloes are used as nodes to construct a unique graph, the MST, that traces skeletal structure. []

January 2020: Naidoo, Krishna, Whiteway, Lorne, Massara, Elena, Gualdi, Davide, Lahav, Ofer, et al (Monthly Notices of the Royal Astronomical Society)

A detailed look at the stellar populations in green valley galaxies

The green valley (GV) represents an important transitional state from actively star-forming galaxies to passively evolving systems. Its traditional definition, based on colour, rests on a number of assumptions that can be subjected to non-trivial systematics. In Angthopo, Ferreras & Silk (2019), we proposed a new definition of the GV based on the 4000 Å break strength. []

January 2020: Angthopo, James, Ferreras, Ignacio, Silk, Joseph (Monthly Notices of the Royal Astronomical Society)

Calculated line lists for H216O and H218O with extensive comparisons to theoretical and experimental sources including the HITRAN2016 database

New line lists are presented for the two most abundant water isotopologues; H216O and H218O. The H216O line list extends to 25710 cm-1 with intensity stabilities provided via ratios of calculated intensities obtained from two different semi-empirical potential energy surfaces. The line list for H218O extends to 20000 cm-1. []

January 2020: Conway, Eamon K., Gordon, Iouli E., Kyuberis, Aleksandra A., Polyansky, Oleg L., Tennyson, Jonathan, et al (Journal of Quantitative Spectroscopy and Radiative Transfer)