This page lists all the PhD projects offered by Astrophysics group, separated according to the following research areas: Galaxies, Massive Stars and Clusters, Low-mass Stars, Star Formation and Astrochemistry, Exoplanets, Cosmology;
The e-MERLIN Cyg OB2 Radio Survey (COBRaS): Mass-loss studies
We plan to co-ordinate, from UCL, the e-MERLIN Cyg OB2 Radio Survey (COBRaS), designed to exploit e-MERLIN's enhanced capabilities to conduct substantial deep-field mapping of the tremendously rich Cyg OB2 association in our Galaxy. The project aims to deliver the most detailed radio census for the most massive OB association in the northern hemisphere. The COBRaS project involves over 30 astronomers from the UK and overseas.
One of the core projects from the Legacy dataset will be to study the radio mass-loss characteristics of substantial numbers of massive stars, including O and early-B type supergiants. The goal is to resolve the current very serious uncertainties in the mass loss and energy feedback processes of massive stars, due to clumped and porous stellar winds.
Recent results have strongly challenged the current model of mass loss via stellar winds, with the enormous consequence that currently accepted mass-loss rates of luminous massive stars may be too high by an order-of-magnitude or more. There is the highest urgency to robustly investigate this discordance since it has far reaching consequences for the evolution and fate of massive stars (which is largely determined by mass loss) and for galactic chemical evolution (where mass loss drives chemical and mechanical feedback on the interstellar medium). The project will involve a range of tasks from e-MERLIN data analysis to NLTE line-synthesis and porosity modelling. Additional mass-loss observations in other spectral regions, including near-IR, mm and Halpha, will also be compared with results from e-MERLIN datasets to study wind clumping, and establish reliable stellar wind parameters.
Contact: Prof. Raman Prinja
(rkp AT star.ucl.ac.uk)
I will be offering several projects on galaxy formation, involving the study of classes of distant galaxies in order to determine their physical properties, such as mass, sizes, kinematics, and star formation properties. The molecular gas in these galaxies, its physical and chemical properties, is of particular interest as this governs the star formation (and thus the formation process) of galaxies.
Contact: Dr Thomas Greve (email@example.com)
Cold gas as a probe of galaxy evolution
One of the biggest impediment in our understanding of galaxy evolution is our relatively poor knowledge of the cycling of gas in and out of galaxies: how gas is accreted onto galaxies, processed into stars, and then returned to the circumgalactic medium. Fortunately, it is now possible to directly observe cold gas in large samples of galaxies and therefore to overcome this difficulty. Cold gas also has the advandage of being a senstive probe of the different mechanisms that can affect the evolution of galaxies. In this project, you will use data from a new large multi-wavelength survey targeting low mass galaxies and robust statistical methods to understand the balance between gas and star formation in these systems. The project, mostly observational in nature, will also include observations at optical, millimeter and radio facilities, high resolution follow-up work with ALMA, and will link with current work in high redshift galaxies which share common properties (low masses and low metallicities).
Contact: Dr Amelie Saintonge (firstname.lastname@example.org; from September 2013 at UCL)
Very Low Mass Metal-poor Stars
So called population III stars which formed in the early Universe have a simplified chemistry due to (near) total absence of elements heavier than helium. If such stars formed with low mass they should still be present due to the very long evolutionary timescales of such objects. There is increasing observational evidence for the existance of low mass, metal poor stars. However it is unclear, to date, how such stars can form in the absence of dust and heavy metals. The project will adapt and make use of a suite of chemical models simulating the formation of low mass stars to investiage such problems.
Molecular line lists for exoplanets and Cool Stars
UCL has been at the forefront of the effort to characterise some of the many extrasolar planets that have been discovered over the last decade. This work requires extensive sets of molecular data to both model observed spectra and as input to model atmosphere codes. Given that many exoplanets are "hot Jupiters" this data must work over extended temperature ranges. At the hot end (T = 1500 - 3000 K) molecular data is also essential for studies of the atmospheres of cool stars and brown dwarfs. The calculation of very extensive line lists using first principles quantum mechanics has been pioneered at UCL were successful datasets have calculated for a number of important molecules (eg water, HCN and H3+) and used for high profile astronomical studies. However there are a number of key systems for which little or no data is available. In particular the hydrogen sulphide (H2S) is thought to be an important constituent of some exoplanets and acetylene (HCCH) molecule is known to be an important constituent of carbon stars. A comprehensive treatment of the spectrum of one of these species at elevated temperatures will be attempted using first principles quantum mechanical methods developed in the group.
Contact: Prof. Jonathan Tennyson (j.tennyson AT ucl.ac.uk)
Star formation and Astrochemistry
How do brown dwarfs form?
Eight out of 10 stars in our stellar
neighbourhood are low-mass
stars (LMSs). The astrophysical importance of brown dwarfs and low-mass stars comes from the fields of
cosmology (are some of these stars primordial?) and Galactic dynamics
(how much mass is stored in faint, low-mass stars?), from the field of
star formation (does the initial mass function vary among star
formation regions, and is there a lower mass limit below which no
"stars" form?) as well as from an area of great current interest, that
of extrasolar planets (what distinguishes a brown dwarf from a
low-mass star, and an extrasolar planet from a brown dwarf?). And yet, the formation of such 'failed' stars is still under debate. This project involves the use of a star formation model to investigate the different proposed scenario for the formation of brown dwarfs. The project is theoretical but can involve an observational component.
Contact: Prof Serena Viti (sv AT star.ucl.ac.uk);
General Project Areas
There are numerous opportunities for research in an exceptionally wide range of activities within this field. Astrochemistry has no preferred scale, so projects range from studies of protoplanetary disks and pre-stellar entities through stellar outflows, dust formation, right up to structure formation in the very Early Universe. In addition, we are engaged in various cross-disciplinary activities, such as laboratory simulations of gas-grain interactions in the interstellar medium (through the Centre for Cosmic Chemistry and Physics) and astrobiology. The various options are far too numerous to list here.
However, as an example, we have a special interest in star-formation studies - the earliest stages of evolution of molecular clouds within the interstellar medium to a young star-forming region. The significance of this is briefly descibed below: Much of the star formation in galaxies occurs in Giant Molecular Clouds. For these regions, knowledge of the interaction and exchange of material between the stars and the interstellar medium is vital to a proper understanding of the mechanisms that drive our Universe and trace its baryonic matter. Observations of molecular emissions from dense gas left over from the star formation process are used to infer the properties of the gas clouds and the nature of the collapse process. This, in turn, can be used to identify the star-formation efficiency and on what it depends.
Within our Group we have considerable expertise and interest in all aspects of the problems we tackle - including the theoretical, modelling and observational activities. Prospective students will therefore be offered a number of possible projects which can include both theoretical and observational components, according to preference.
Molecular line lists for characterising extrasolar planets
The number of extrasolar planets detected is increasing rapidly and attention is turning to determining what they are made of. To do this requires very significant quantities of spectroscopic data which is largely unavailable. A major new project is being launched at UCL to calculated a comprehensive set of molecular line lists that will allow scientists to model the atmospheres of hot exoplanets, brown dwarf and cools stars (see www.exomol.com).
One (or possibly two) PhD students are sort to work in a team of about 6 people on this project. Interested students should have a good understanding of quantum mechanincs and be interested in computational work. The studentships are available to both UK and EU nationals.
Contact: Prof Jonathan Tennyson
General Project Areas (3-yrs)
The past decade has seen a revolution in cosmology underpinned by an array of precision observational probes, painting a picture of a Universe consisting of roughly 4 per cent ordinary matter, 21 per cent "cold dark matter" and 75 per cent even more mysterious "dark energy". The UCL cosmology group has a wide range of interests, spanning from the basic properties and evolution of the large scale structure in the Universe all the way back to the initial fluctuations that seeded this structure. We use observational and theoretical tools as well as numerical simulations to tackle fundamental questions posed by the current cosmological model, for example: Does the dark energy density vary with cosmic time? What is the fundamental physics that sets the initial conditions of the universe? What can the clumpiness of the dark matter tell us about it's nature? However we also try to challenge the current model and investigate alternatives, such as the possible breakdown of general relativity at cosmological scales, and exotic physics operating at the ultra high energy scales present in the early universe.
Current research includes: exploitation of a major ongoing
Hubble Space Telescope survey of galaxy clusters (HST-CLASH);
measurement of the clustering and alignment of galaxies in
current galaxy surveys (SDSS, WiggleZ) and in N-body
simulations; the use of galaxy redshift surveys to measure the
baryonic, cold dark matter and neutrino contents of the
Universe, and to estimate the distribution of galaxies in
relation to the dark matter; analysis of gravitational lensing
data to measure the distribution of the dark matter; the
reconstruction of the primordial power spectrum at a variety of
scales using different data sets and linking this to early
universe physics; testing fundamental cosmological assumptions
such as Gaussianity and Isotropy. We are also involved in ESA's
Planck cosmic microwave background satellite, which began
scanning the microwave sky (from the distant second Lagrange
point of the Earth-Sun system) in Sept 2009. The satellite has
already completed a full survey of the microwave sky, providing
a leap forward in resolution, sensitivity, and frequency
coverage, and a second survey is now under way. This data will
provide vital clues to the physics at ultra high energy scales
that powered the Big Bang. It can also be cross-correlated with
galaxy surveys to provide unique information about the nature
of dark energy, and test Einstein's general relativity at
We are heavily involved in designing the next generation of
surveys which will lead to dramatic improvements in our
understanding of the Universe in the next two decades. In
optical imaging surveys, we are designing methods to extract
photometric redshifts in order to obtain distances to several
millions of galaxies. In the radio, we are involved in
simulating how future radio telescopes will observe the 21 cm
radiation in the dark ages of the universe, as well as the 21
cm radiation present in most galaxies in the nearby Universe.
In about a decade this should be the largest survey (billions
of galaxies) available to probe dark matter and dark energy. In
particular: the Dark Energy Survey (DES) which has first light in 2012;
Euclid, an ESA satellite proposal to measure the nature
of dark energy; and the Square Kilometer Array (SKA) which will
revolutionize our understanding of reionization using 21 cm
There are many possible PhD topics within the above areas and
the exact PhD project would emerge from joint discussions
between the successful candidate and the contacts.
Given that Planck has a full sky survey in hand and DES has seen its first light in September 2012, it is an exciting time to do a PhD
in cosmology at UCL.
The following give example projects:
(i) ESA's Planck satellite is dramatically improving measurements of the cosmic microwave background (CMB), with several full sky surveys of data in hand and the first CMB data due to become publicly available in early 2013. The CMB contains primordial ripples in the early universe - signatures of physics at very high energies, inaccessible to terrestrial particle accelerators. The first aim of the project is to use the Planck data to uncover fingerprints of these extreme physics, and thereby probe the physics of the origin of structure. Further, the current accelerated expansion of Universe, thought to be due to the mysterious “dark energy” or a modification of Einstein’s General Relativity, is one of the biggest puzzles of physics. The physics that describes the initial conditions and the physics that describes the late-time universe have to be self-consistent for the whole to make sense. One of the primary ways of testing this consistency is to combine CMB data with tracers of the large scale structure of the universe, such as galaxy surveys. The international Dark Energy Survey (DES), which was initiated and planned with leadership from UCL, saw “first light” in Oct 2012. The second aim of the project is to combine this survey together with Planck to provide a window into the "early" and "dark" physics of the universe.
(ii) The Square Kilometre Array is a future telescope which will be able to locate more than a billion galaxies in the sky by looking at their neutral Hydrogen content. This dataset would measure to unprecedented accuracy the properties of dark energy as well as test Einstein's theory of general relativity at large scales to unprecedented accuracy. It will provide us with the most accurate dataset for measuring cosmology. However one of the greatest challenges that we face in the coming years is to understand the content of HI in the high redshift in order to be able to perform these cosmological measurements. Several pathfinders to this huge telescope will start paving the way in coming years. An example project would be to use simulations of optical and radio images to attempt to extract the most information of the next generation of radio telescopes for cosmology which will happen in the next years. This will pave the way to what the SKA will be able to teach us in the next decade.
(iii) One potential project would be on extracting cosmological constraints from the new Dark Energy Survey (DES) data on large-scale structure and/or weak gravitational lensing. Ofer Lahav is the UK lead of DES and is Chair of the international Science Committee. Sarah Bridle is Co-lead of the international DES Weak Lensing Working Group and Filipe Abdalla is Co-lead of the DES Spectroscopic Task Force. DES had first light in September 2012 and we expect to have the first set of observations in 2013. Example sub-projects would be (i) to accurately measure the distances to galaxies using photometric redshifts and a small spectroscopic redshift calibration sample, (ii) to constrain the mass of the neutrino using the clustering of galaxies and/or (iii) to test General Relativity by comparing gravitational lensing with galaxy clustering.
There are many possible PhD topics within the above areas and the exact PhD project would emerge from joint discussions between the successful candidate and the contacts.
Given that Planck has a full sky survey in hand and DES had first light in 2012 it is an exciting time to do a PhD in cosmology at UCL.
Please see our UCL cosmology web page for further information.
The 21cm neutral hydrogen radiation from the first stars and quasars
The LOFAR array has been now comisioned and is currently producing data on
its shallow Million Source Sky Survey the MSSS. Shortly after it will
start producing data for the individual Key science projects one of which
is hunting for the epoch of reionisation. This project will be hunting for
the signal imprinted onto the 21cm neutral hydrogen radiation from the
first stars and quasars formed in the Universe. An example project would
use data from this survey to look for statistical significant detection of
this signal in the radio part of the spectrum.
Contact: Dr Filipe Abdalla (fba AT star.ucl.ac.uk)
Understanding the origin of structure in the Universe
The early universe is a “laboratory” for testing physics at very high energies, up to a trillion times greater than the energies reached by the Large Hadron Collider. The origin of structure in the universe is deeply tied to this extreme physics, which is imprinted in the primordial ripples seen in the cosmic microwave background (the leftover heat of the Big Bang), and the large scale structure of the universe traced by galaxies. The main purpose of the project is to understand the physics of the early universe, creating innovative algorithms to exploit novel observables, and applying them to next generation CMB data from Planck and large scale structure data, especially DES. The student will be part of the European Research Council Starting Grant Project CosmicDawn. More information about early universe cosmology at UCL can be found here.
Contact: Dr Hiranya Peiris (h.peiris AT ucl.ac.uk)
Galaxy formation as a probe of fundamental physics
Galaxies are the fundamental building blocks of the universe. Their internal structure provides critical tests of the dark matter paradigm; they are responsible for the reionisation of the universe; and their distribution on cosmological scales is a key discriminant between competing theories of, for example, dark energy. But extracting the desired information requires a better understanding of the combined dynamics of dark matter, gas and stars in a cosmological setting. As part of an international collaboration, this project will explore the ever-shifting interface between theory, observation and computation. There are opportunities to focus on the galaxy formation physics, on metal enrichment of the intergalactic medium, or on the application of new ideas in these areas to galaxy survey design and exploitation.
Contact: Dr Andrew Pontzen (currently email@example.com, but at UCL from September 2013)
Page last modified on 15 mar 13 12:12 by Alexandra N D Fanghanel