PhD Projects

Exoplanet discoveries of the last 30 years have taught us the planets are far more common and diverse than our Solar System led us to believe. From the original Hot Jupiters to the ubiquitous sub-Neptunes and the mysterious super-Earths, many problems about the origin and evolution abound. With the successful launch of JWST and the upcoming ARIEL mission, we now have a new way to explore exoplanets: by observing the properties and composition of their atmospheres. However, these new observations can only be interpreted in the framework of any theoretical model. At the moment, there is yet to be a clear picture of what knowledge of the composition of an exoplanet's atmosphere tells us. The structure, composition, cloud properties and dynamics of exoplanet atmospheres need to be better understood with many open theoretical problems. In this project, you will use analytical, numerical, and simulation methods to tackle these challenges head-on, guided by results from state-of-the-art JWST observations. Given the large number of open theoretical problems, you will be free to develop your research direction.

The Euclid space telescope, which launched successfully in July 2023, is in the process of surveying one third of the sky, during which it will produce a catalogue with billions of detected astronomical sources. A few hundred of these will be quasars in the early Universe, seen as they were less than a billion years after the Big Bang, some of which will be beyond the current record of redshift z = 7.5. On the timescale of a PhD starting in October 2024 Euclid data will allow us to push our understanding of the quasar population back to redshift 9, which in turn will reveal the nature of the first super-massive black holes; this project will be based on the interpretation and analysis of this new data. As such the project sits at the interface between astronomy, statistics and data science, so would suit a student interested in these areas.

Stellar magnetic activity introduces uncertainties and biases in the determination of exoplanet parameters, and disentangling the stellar from the planetary signal is critical if we want to study exoplanets. As stellar magnetic activity also leaves a trace in stellar spectra (through changes in spectral line shape and strength, as well as by modulating stellar granulation signals, stellar limb darkening and broad-band emergent intensities), it should be possible to remove the stellar signal from the planetary signal. The aim of this project is to do just that by identifying reliable tracers of stellar activity and developing models to remove the stellar from the planetary signal. You will be using radiative transfer codes to derive the emergent radiation from (magneto-convection) models of stellar surfaces with a range of activity levels.

With its Legacy Survey of Space and Time (LSST), the Rubin Observatory (first light in 2027) will provide the widest and deepest measurements of the clustering and gravitational lensing of galaxies to date. Thanks to its high cadence, Rubin will also revolutionise transient science, for example detecting hundreds of thousands of supernovae type Ia. This PhD project will tackle the challenges of modeling the spatial distributions of the detected high-redshift galaxies and supernovae at the precision needed to harness their cosmological information. This will require developing innovative techniques to model and accurately propagate potential systematic uncertainties all the way from the processing of photometric images to the extraction of cosmological parameters. Machine learning is likely to play a big role in making these techniques computationally efficient, for example in accelerating image processing or simulations. Data from Rubin-like precursor surveys such as Hyper Supreme Cam Survey and the Dark Energy Survey will be employed as a testbed, in combination with valuable information (e.g., CMB lensing) from CMB experiments such as the Atacama Cosmology Telescope and the Simons Observatory.

This PhD project will study the formation of planets in the inner regions of protoplanetary disks. Specifically, it will focus on modelling the growth of planetesimals and planetary embryos into full-fledged planets in the inner disk, via N-body simulations supplemented with the effects of interactions with gas. The successful applicant will have a strong background in undergraduate physics, including a solid understanding of undergraduate-level hydrodynamics, and good programming skills (e.g., in python).

Over the last 30 years 5500 extrasolar planets have been found orbiting stars beyond our solar system, with the vast majority orbiting extremely close to their host stars. These discoveries have fundamentally challenged our understanding of planet formation and evolution. Theory predicts that an exoplanet’s atmospheric composition depends on how and where the planet formed and that the extreme radiation suffered by close-in exoplanets leads to strong atmospheric winds and atmospheric loss. To robustly test these theories requires observations of the planets with the largest signals, “hot Jupiters”, which will pave the way for future observations of Earth-sized exoplanets. This project will combine the revolutionary sensitivity of the James Webb Space Telescope (JWST) with Hubble and ground-based data to measure the chemical compositions of hot Jupiters in unprecedented detail. In doing so, the project will perform robust tests of how and why hot Jupiters came to be and how their atmospheres respond to extreme irradiation.

The Herschel Space Observatory has revealed that galaxies containing substantial amounts of dust obscured star formation, so-called Dusty Star-Forming Galaxies (DSFGs), play a major role in the evolution of the galaxy population. However, these objects are hard to study in the optical and near-infrared since the large amounts of dust within them absorb light at these wavelengths and re-emit it at longer far-IR and submm wavelengths. Surveys with Herschel have revealed the DSFG population at large redshift, z~2-4, with some exceptional objects at still higher redshift. Studying these objects and determining their properties at other wavelengths will allow us to place them in the broader context of galaxy and large scale structure evolution: do they, for example, evolve into massive elliptical galaxies, and if so, do they lie in galaxy clusters or protoclusters at high redshift? What triggers their star formation activity - is it the result of galaxy interactions and mergers, as seen in the local universe, or are other factors such as cold gas flows from the cosmic web involved? What is their relationship to quasars and other types of active galaxy - in the local universe galaxy mergers are thought to trigger quasar-like activity; is this true for the Herschel high redshift DSFGs? What is the role of gravitational lensing in our view of these objects, and can this be used to study the less luminous but far more numerous underlying population of dusty galaxies? New data from our own observations and from large projects such as Euclid and JWST surveys will be used to answer these questions.

At the same time, new insights into the DSFGs’ local counterparts, Ultraluminous Infrared Galaxies (ULIRGs), are becoming possible thanks to the new generation of submm instruments. Recent observations led by the Imperial Infrared group have detected polarised dust emission in the core of the nearest ULRG, Arp220, suggesting the presence of magnetic fields at the heart of this object. Is this true for other local ULIRGs, and what are the implications for these rapidly star forming galaxies?

Meanwhile, a new generation of far-IR space missions are being proposed to NASA. Simulations and predictions of what these missions might find are needed to help develop their science cases and optimise their instruments. Our observations of DSFGs near and far will feed into this process and help set the scene for far-IR astronomy in the 2030s and beyond.

• Exoplanets origins and evolution - Dr James Owen
• Accretion discs around polluted white dwarfs - Dr Chris Manser and Dr James Owen
• Atmospheres of Habitable Zone Exoplanets around M dwarfs - Dr Subhanjoy Mohanty
• Epoch of Reionization with REACH and SKA - Dr Jonathan Pritchard 
• Cosmology with the CMB - Prof Andrew Jaffe and Prof Alan Heavens
• The most luminous galaxies in the local Universe - Dr Dave Clements
• Astrophysics 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 a5 Emulating radiation from variable stars - Dr Yvonne Unruh nd 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
•  The most luminous galaxies in the local Universe - Dr Dave Clements
• Pushing the limits of high-z LSS structure cosmology - Dr Boris Leistedt
•  Emulating radiation from variable stars - Dr Yvonne Unruh
• Cosmology with likelihood-free inference - Prof Alan Heavens
•  The highest redshift quasars - Professor Stephen Warren
• Planet Formation in the Inner Disc-The First End to End Model - Dr Subu Mohanty
• Stellar Brightness Variability and Exoplanets – Dr Yvonne Unruh
• The Earliest Stages of Planet Formation - Dr Richard Booth
• Molecules in the Atmosphere of Venus - Dr David Clements and Dr Ingo Mueller