Projects on offer for 2021 entry will be progressively added here in December. The projects themselves may evolve somewhat before October 2021.
Pushing the limits of high-redshift large-scale structure cosmology - Dr Boris Leistedt and Dr Daniel Mortlock
The 2020s will be exciting for observational cosmology with the Vera Rubin Observatory LSST camera and the Euclid satellite surveying billions of galaxies and mapping the large scale structure of the universe at unprecedented accuracy. The fiducial analyses planned with those surveys will exploit standard populations of galaxies up to intermediate redshift (~1-2), which will be invaluable for a range of cosmological studies, in particular for probing the nature of dark matter and dark energy. However, those populations are not competitive when it comes to constraining early-universe physics, which gets imprinted into the largest observable scales in the universe. Yet, those scales can be probed using more exotic objects such as quasars and Lyman break galaxies, detectable at high redshifts (~4-5) in LSST data, for example. This project aims at unlocking the potential of those populations and placing new limits on large-scale signatures of early universe physics. In order to connect those with the large, complex data sets available, this project will involve a balance of theory, modeling, and data analysis, leveraging advanced statistics and machine learning methods.
The highest redshift quasars - Professor Stephen Warren
The most distant quasars, at redshifts z>7, are very valuable for learning about cosmic reionisation and the formation of supermassive black holes. This project will include preparatory work leading up to searches for 7<z<9 quasars with the Euclid satellite, to be launched in 2022, and consideration of the science that can be achieved with the Euclid surveys.
Dusty Starforming Galaxies in Protoclusters - Dr Dave Clements
Observations at far-IR and submm wavelengths have identified forming galaxy clusters, so called protoclusters, as clumps of far-IR/submm sources. These are dusty star forming galaxies. The star formation rate in these nascent clusters is dominated by these dusty star forming galaxies (DSFG), which appear to be going through a brief burst of star formation. Quite what triggers the simultaneous high star formation rates in these sources is unclear, and the broader role of such DSFG dominated protoclusters in the broader context of cluster and galaxy formation is poorly understood. Current models of galaxy and cluster formation fail to explain the high star formation rates seen in these objects. This observational project will use telescopes at a wide range of wavelengths to study these star forming protoclusters, examine the physics behind their star forming activity, and determine how these systems fit into the broader picture of galaxy and cluster formation.
The Most Luminous Galaxies in the Local Universe - Dr Dave Clements
The most luminous galaxies in the local universe are the Ultraluminous Infrared Galaxies. These were first discovered by IRAS in the mid-80s, but they are still a major target of observational research today, at least partly because they seem to be the local equivalents of the high redshift dusty star forming galaxies being uncovered in unexpected numbers by Herschel. This project aims to deepen our knowledge and understanding of these systems through the use of existing data eg. from Herschel and Akari, and through the acquisition of new data. A key resource for this project will be the HERUS (Herschel ULIRG Survey) dataset on local ULIRGs. Aims for this project include determining the physical environment in the starburst regions powering ULIRGs, seeing what effect these conditions have on massive star formation, fitting spectral energy distribution models to the broad-band spectra of these objects, examination of selection biases that may affect our comparison of local and high redshift populations, and the production of submm spectral line surveys for these objects using archival and, possibly, new observational data.
Emulating radiation from variable stars - Dr Yvonne Unruh
The change in stellar brightness due to magnetic activity is one of the main nuisance parameters in the study of exoplanet atmospheres and plays an important role in star-planet interactions. The aim of this project is to calculate the emission from (existing) magneto-convection simulations of active stellar surfaces for a range of stars and activity levels. These will allow us to remove the stellar-activity contamination from exoplanet transit observations. The emphasis here will be on obtaining realistic intensity spectra at UV wavelengths where some of the usual simplifying assumptions such as local thermodynamic equilibrium (LTE) can no longer be used for the radiative-transfer calculations of the spectra.
The radiative-transfer calculations that are needed to produce realistic spectra in the UV have to take into account non-LTE effects, making them too expensive to capture to sample the grid sizes and resolutions that are needed to capture the interaction of the magnetic fields with the stellar surface convection. We will thus explore whether it is possible to develop a ML emulator that allows one to infer intensity spectra from a limited grid of stellar atmospheres to which the full non-LTE calculations can be applied.
Astrophysics and cosmology from the 21cm line - Dr Jonathan Pritchard
One of the last frontiers of astrophysics is the first billion years of the Universe, when the formation of the first galaxies and black holes produced the first star light leading to a Cosmic Dawn. Observations of the 21 cm line of neutral hydrogen in the radio promises to open a window onto this period (z=6-27) for the first time. Interferometers like LOFAR, HERA, and SKA will map fluctuations in the 21cm signal, while single dipole experiments like EDGES and REACH hope to detect the all sky global signal. These new experiments are expected to provide new insights into astrophysics and cosmology and are already starting to provide interesting data. The student will be part of a collaboration preparing for SKA observations and thinking about the analysis of REACH to develop new statistical and modelling techniques for 21cm experiments.
Cosmology with likelihood-free inference - Prof Alan Heavens
Cosmology from the late-time Universe is complicated because gravitational instability skews the matter distribution away from its original gaussian random field. Dealing in a statistically principled way with non-gaussian fields is a challenge. One of only a few methods which look promising is likelihood-free inference (LFI), which relies on forward simulation of observed data, and usually extreme data compression. The project would investigate this in the context of weak gravitational lensing, and would involve some algorithmic development on both LFI and data compression, and may use some machine learning techniques, for preparation for application to Euclid and LSST data.
Exoplanet Origins and Evolution - Dr James Owen
The last decade has seen an explosion of exoplanet detections. We now know most stars host a planetary system; however, these exoplanetary systems are incredibly diverse and unlike our Solar-System. Using the ALMA telescope, we have been able to image the planet-forming environments (protoplanetary discs) at unprecedented resolution and sensitivity. These images have revealed that these protoplanetary discs are being shaped and disrupted by planets forming within them. However, linking the properties of planet-forming discs to the observed exoplanet population remains an unsolved theoretical problem. This project involves building theoretical models of how forming planets will interact with their parent protoplanetary discs and linking them to current observations (see Picture). This project will allow the student to undertake sophisticated hydrodynamical computer simulations of planet formation, and/or become involved in state-of-the-art observations.
Past projects have included
- Emulating radiation from variable stars - Dr Yvonne Unruh
- Exoplanets origins and evolution - Dr James Owen
- The most luminous galaxies in the local Universe - Dr Dave Clements
- Astropysics and cosmology from the 21cm line - Dr Jonathan Pritchard
- Cosmology with the next generation of CMB experiments - Prof Andrew Jaffe
- Planet formation and habitability - Dr Subu Mohanty
- The first quasars and supermassive Black Holes - Dr Daniel Mortlock
- Bayesian Analysis of the dynamic Universe - Dr Florent Leclercq and Prof Alan Heavens
- Bayesian analysis of weak gravitational lensing - Prof Alan Heavens and Prof Andrew Jaffe
- Searching for the most distant quasars - Dr Daniel Mortlock
- Higgs, Dark Matter and the Global Search for Physics beyond the Standard Model - Dr Pat Scott
- Direct Detection of Dark Matter and Global Fits - Prof Roberto Trotta
- Cosmology and Fundamental Physics with Euclid - Prof Roberto Trotta
- Extreme Dusty Star-Forming Galaxies - Dr Dave Clements
- The Nature and Evolution of 70 micron selected galaxies - Dr Dave Clements
- The X-ray-Starburst Connection in the Herschel Era - Dr Dave Clements
- Advanced statistical methods for astrophysical probes of dark energy - Prof Roberto Trotta
- The early Universe and cosmological parameters from the Cosmic Microwave Background, Gravitational Waves, and other observations - Professor Andrew Jaffe
- Determining the topology of the Universe from the Cosmic Microwave Background - Professor Andrew Jaffe
- Accretion Disks, Planet Formation and Habitability Around Red and Brown Dwarfs - Dr Subu Mohanty
- Towards optimal statistics of reionization and the 21 cm signal - Dr Jonathan Pritchard
- Cool pre-main sequence stars: their surfaces and circumstellar environments - Dr Yvonne Unruh
- Understanding solar brightness changes on climate-relevant time scales - Dr Yvonne Unruh
- Gravitational lensing, dark matter, and black holes - Professor Steve Warren
- Exoplan et origins and evolution - Dr James Owen