Galaxies, Active Galactic Nuclei and Cosmology

Supervisory Team: Kristen Coppin, Jim Geach

Over half of the star formation energy generation in the Universe is extincted at optical wavelengths and enshrouded by dust which absorbs and re-radiates the starlight in the far-infrared/submm; and the sub-mm and mm atmospheric windows allow us to access the redshifted far-infrared emission from this obscured or ``hidden’’ side of galaxy formation and evolution.

The James Clerk Maxwell Telescope (JCMT) Cosmology Legacy Survey (S2CLS; Geach et al. 2017) and its extension via the SCUBA-2 COSMOS survey (S2COSMOS; Simpson et al. 2017) and now S2XLS (PI Geach) and STUDIES (Wang et al. 2017) are the largest and most sensitive and ambitious single-dish surveys at 850 and 450 micron (in the submm wavebands) ever conducted.  In addition, the 50-m Large Millimeter Telescope in Mexico will at some point be conducting unique and transformative imaging of the sky at millimeter wavelengths through a series of public Legacy Surveys (Ultra-Deep and Large Scale Structure surveys in particular) using the new TolTEC camera (http://toltec.astro.umass.edu).  These unprecedented legacy surveys have been yielding thousands of high-redshift galaxies selected in the sub-mm/mm wavebands - providing an order-of-magnitude improvement in the sample sizes of previous surveys at these wavelengths!

With so much data now in-hand there are several possible projects that could be carved out using a combination of these legacy (sub)mm surveys with existing ancillary multi-wavelength data to make progress on a key outstanding question in galaxy evolution: How are dust and metals built up in massive galaxies over cosmic time?

The first project the student would start with involves new high-precision ALMA 870um continuum observations following up the largest statistically significant sample (~17) of the rarest and brightest such “submillimetre-selected” galaxies from a single contiguous survey (the SCUBA-2 eXtremely Large Survey (S2XLS; Garrett et al. 2023), enabling a systematic study of the nature of the rare bright end of this population for the first time.  The project will require the student to use existing public state-of-the-art datasets spanning radio-to-Xray wavelengths (incl spectroscopic redshift data) in order to obtain the panchromatic Spectral Energy Distribution (SED) of each SMG.  This will enable detailed measurements of physical quantities for each source, such as photometric redshift, stellar mass, dust mass, IR luminosity, total star formation rate, etc. in order to reveal the nature of these rarest and brightest submillimetre galaxies.  In addition, some of the SMGs are likely to be gravitationally lensed, which would require the use of lensing models to determine the intrinsic properties of some fraction of these SMGs.Other projects that could be explored after the initial plan include 1) Measuring the morphologies and SEDs of the dustiest SMGs identified in the surveys above with existing public JWST CEERS data; or 2) performing a systematic study of locating and probing the high-redshift tail of the distribution of (sub)mm galaxies (via new mm observations with ToLTEC).  We are also involved in ongoing efforts to perform detailed follow-up of these high-z submm-detected sources at higher resolution with the Atacama Large Millimetre Array (ALMA) situated at 5000m on the Chajnantor plateau in Chile.  It is envisaged that the findings of this work will feed naturally into new ALMA and other telescope proposals (eg. JWST).

Supervisory Team: Dan Smith, Luke Holden, Soumyadeep Das

The evolution of galaxies is to a significant extent driven by the complex interplay between star formation and “feedback”. Feedback can refer to multiple physical processes: it can refer to high mass stars going supernova at the end of their short lives and impacting on a galaxy’s gas supply (the fuel for star formation), or to the coupling between the gas physics and the energy released by accretion onto a galaxy’s nuclear supermassive black holes. It can also take different forms – either ejecting gas from a galaxy altogether and in doing so quenching the star formation, or maintaining a passive galaxy by preventing gas from cooling out of it’s hot halo.

In this context, we are entering a golden age of radio astronomy, with the capabilities (sensitivity, resolution and survey speed) of new interferometers such as LOFAR expanding rapidly in comparison to previous generations, to an extent that will not be surpassed in the coming decades. Radio astronomy is uniquely suited to the study of feedback and galaxy growth since the faint radio source population is known to be a mixture of sources dominated by star formation, and by accretion onto supermassive black holes. But which source falls in which category, and how much each process contributes to the overall cosmic energy budget is impossible to quantify on the basis of radio data alone.

The best way to answer these questions is using massively multiplexed spectroscopy of radio sources, and one of the key science goals of the WEAVE-LOFAR survey – which is now beginning on a five-year programme to obtain a million spectra of LOFAR sources from the Canary Island of La Palma – is to investigate exactly this issue. As well as yielding precise redshifts, optical spectroscopy can reveal the luminous signatures of star-formation and accretion underway in radio sources, and the survey has been designed with this kind of population study in mind.

With the WEAVE-LOFAR survey starting in late in 2025, the timing is perfect for a PhD student starting in October 2026 to come in and write some of the first – and most exciting – papers on galaxy and AGN co-evolution using this transformational data set. If this sounds like something that you would like to do, please get in touch and we can discuss how we might work together.

Supervisory team: Martin Bourne, Martin Hardcastle, Sophie Koudmani

Supermassive black holes (SMBHs) were already active in the early universe, launching powerful relativistic jets that profoundly influenced their surroundings. These early active galactic nuclei (AGN) are likely to have played a key role in regulating the growth of early galaxies, driving large-scale outflows, and magnetising the intergalactic medium. Yet, how jet-driven feedback operated under the extreme physical conditions of the early Universe, where gas was denser and more irregular, and the cosmic microwave background (CMB) energy density was much higher, remains poorly understood. Recent observations of giant radio galaxies at high redshift (e.g., Oei et al. 2024) provide tantalising evidence that jet feedback could reach vast scales. However, how such powerful jets are produced and maintain coherence across such large distances remains an open question.

This project will explore the physics of high-redshift AGN jets and their impact on galaxy and halo evolution using a suite of next-generation magnetohydrodynamic (MHD) cosmological zoom-in simulations with the moving-mesh code AREPO. These simulations will follow, at high resolution, the propagation and evolution of jets within realistic, evolving environments at high redshift, capturing the interplay between jet power, ambient gas density, and magnetic-field structure across a vast range of scales. The student will investigate how jets behave in the high-redshift Universe, how giant radio galaxies can reach such enormous sizes, and how their energy is transported and dissipated from galactic to cosmological scales.

As part of this project, the student will generate and analyse synthetic radio observations tailored for SKA and LOFAR. These will be produced directly from the simulations, incorporating synchrotron emission and spectral ageing to model how jet-inflated lobes evolve and fade with time. At high redshift, energy losses through inverse-Compton scattering off the CMB become dominant, dramatically reducing radio surface brightness and steepening spectra. The student will quantify how these CMB-driven losses alter the observed morphology and luminosity of jets and lobes, and will determine under what conditions large, powerful radio galaxies can still be detected in deep surveys. Beyond radio diagnostics, the simulations will also be used to study the thermodynamic impact of jet feedback on the surrounding hot gas and to track the amplification and evolution of magnetic fields within and around the lobes. This will help constrain how AGN contribute to magnetising the circumgalactic and intergalactic medium at early epochs. Together, these analyses will establish a physically motivated framework for interpreting the radio properties of high-redshift AGN and for identifying the conditions that enable the formation of giant radio galaxies in the young Universe.

Supervisory team: Martin Bourne, Sophie Koudmani, Vid Irsic, Sugata Kaviraj

Large cosmological simulations have revolutionised our understanding of galaxy formation and evolution, yet a major uncertainty remains: how to model the feedback from supermassive black holes accurately across the vast range of scales involved. While large cosmological simulations capture the assembly of galaxies over cosmic time, the physical processes that launch and couple active galactic nucleus (AGN)–driven outflows occur on parsec or sub-parsec scales, far below their resolution. Current prescriptions are necessarily simplified, and while they reproduce some key observables, they often lack a clear physical connection to the processes revealed by high-resolution simulations. Bridging this scale gap is essential for developing predictive models of black hole and galaxy co-evolution.

This project will focus on building that missing connection across the galaxy population, up to group and cluster scales. Using results from state-of-the-art, high-resolution simulations of AGN jets, disc-driven winds, and radiative feedback, the student will investigate how these outflows interact with multiphase gas across a range of galaxy and halo masses, feedback powers, and orientations. By quantifying how energy and momentum are injected into the surrounding medium and how this coupling depends on local conditions such as gas density, temperature, magnetic fields, and velocity structure, the project will establish the physical basis for improved feedback models and for comparing the impact and relative importance of jet-, wind-, and radiation-driven feedback across different environments and scales.

Subsequently, these physically motivated relations will be implemented as new sub-grid prescriptions within the AREPO cosmological simulation code. The student will run controlled experiments, first in isolated galaxy models and then in small cosmological volumes, to calibrate and test these prescriptions. By comparing outcomes such as galaxy stellar masses, black-hole growth, and circumgalactic gas properties against the original high-resolution runs, the work will assess how well the sub-grid model captures the key physics at coarser resolution. Depending on progress and interest, the project could then be extended to incorporate the effects of multiphase outflows into cosmological simulations or to explore data-driven and machine-learning approaches for adaptive feedback modelling.

The resulting models will be used to study the long-term co-evolution of black holes and galaxies, tracing how small-scale feedback physics shapes the environment on galactic and cosmological scales. The simulations will provide a crucial theoretical framework for interpreting multi-wavelength data from a range of observational missions, including JWST, Euclid, ALMA, and SKA, and for connecting the physics of AGN feedback to the observed evolution of galaxies across cosmic time.

Supervisory team: Martin Krause, Darshan Kakkad

Galactic outflows are an important ingredient for understanding the evolution of galaxies, possibly influencing the growth of some galaxies and transporting metals and magnetic fields into the intergalactic medium. One of the main difficulties in diagnosing galactic outflows is to link the driving high-energy plasma, which is typically produced by AGN jets or supernovae, tenuous and hard to observe, to optically well-observable cold clouds, often entrained in outflows. Complex hydrodynamic processes govern the formation, shearing and evaporation of such clouds. This project will produce 3D hydrodynamic simulations to replicate the turbulent conditions in such outflows and the different gas phases involved. The goal is to determine the physical conditions outflows must have to allow for a given observational signature (mass, temperature, velocities) of the entrained cold clouds. Depending on the interest of the student, the project could move more into the direction of generating their own simulations or more into comparison to available observational data.

Knowledge of hydrodynamics and some prior experience with simulation codes are beneficial, but can also be acquired at the beginning of the project.

Supervisory team: David Lagattuta, Alyssa Drake, Jim Geach

Galaxy clusters are ideal laboratories for studying the Universe. Forming at nodes of the cosmic web (the large-scale structure that makes up the backbone of everything we see) clusters have large physical sizes, span a wide range of environments, and contain significant quantities of both baryons and dark matter. Because they are so massive, many clusters warp the fabric of spacetime around them, becoming what are known as gravitational lenses. Lenses enhance our understanding of the Universe in two key ways, by 1.) magnifying distant objects behind them (becoming the Universe's largest telescopes) and 2.) providing insight into the distribution and properties of (otherwise invisible) dark matter.

In this project we will investigate galaxy clusters acting as gravitational lenses using a powerful combination of high-resolution imaging and spectroscopy. This will allow us to simultaneously model their structures and identify highly magnified, incredibly distant galaxies behind them. Doing so, we will learn about both the nature of dark matter and galaxy evolution in the early Universe.

In particular, we will take advantage of two large, new cluster data sets: a.) Kaleidoscope, a spectroscopic survey targeting clusters with the Multi-Unit Spectroscopic Explorer (MUSE), an integral-field spectrograph on the VLT, and b.) SLICE, a multi-band imaging campaign on the James Webb Space telescope (JWST). The combination of these data sets unlocks incredibly robust information about the clusters and everything along their lines of sight, providing a unique, 3D picture of mass buildup, structure formation, and galaxy evolution.

Because of this, this PhD project offers a great deal of flexibility and opportunity to explore a wide variety of topics deeply tied to fundamental elements of Astronomy and Astrophysics.

Supervisory team: Vid Irsic, Dan Smith

The large-scale structure of the Universe encodes fundamental information about dark matter's nature. While cold dark matter (CDM) successfully explains structure on large scales, significant uncertainties remain about dark matter's particle properties. Ultra-light dark matter (ULDM), with masses around 10^-22 to 10^-21 eV, suppresses structure formation below scales set by quantum pressure, potentially resolving tensions between CDM predictions and observations of dwarf galaxies. Warm dark matter and self-interacting dark matter similarly predict testable modifications to the matter power spectrum.

The neutral hydrogen (HI) distribution traced by the Lyman-alpha forest probes the matter field during galaxy formation (z ~ 2-4), where different dark matter models make divergent predictions. This project will leverage cross-correlations between the Lyman-alpha forest and high-redshift quasars to constrain dark matter properties from the DESI survey data. The project would involve building on the existing methodology resulting in improved measurements, as well as the interpretation of the results. The second part of the project would leverage this methodology to also explore cross-correlations between the Lyman-alpha forest and high-redshift Lyman-break galaxies (LBGs). These cross-correlations combine continuous three-dimensional matter mapping from Lyman-alpha absorption with galaxy clustering measurements, enabling precise tests on scales (k ~ 1-10 h/Mpc) where ULDM signatures emerge.

The student will develop data analysis techniques for large spectroscopic datasets from the currently operating DESI survey, with applications to future surveys including DESI-II and the Wide-field Spectroscopic Telescope (WST). The measurements will be compared with theoretical models of structure growth to place independent constraints on deviations from standard cosmology. By mapping structure evolution from the first galaxies through the peak of star formation history, this work establishes a new observational window for testing dark matter scenarios and potentially revealing new physics in the dark sector. The student will join the international DESI collaboration.

Supervisory team: Vid Irsic, Martin Bourne, Sophie Koudmani, Sugata Kaviraj

The co-evolution of supermassive black holes and their host galaxies remain hotly debated, particularly regarding how Active Galactic Nuclei (AGN) feedback redistributes baryonic matter. Recent cosmological clustering analyses reveal small-scale discrepancies suggesting feedback operates more vigorously and over larger distances than traditional models predict (Martin-Alvarez et al. 2024; Bigwood et al. 2025; Hadzhiyska et al. 2025). These hints indicate that AGN activity imprints should be detectable in the gas distribution surrounding galaxies and throughout galaxy groups and clusters.

This project will investigate AGN feedback through Sunyaev-Zel'dovich (SZ) effects — powerful probes of hot ionized gas. While the thermal SZ effect traces integrated electron pressure, the kinetic SZ (kSZ) effect is sensitive to electron momentum, making it invaluable for detecting outflows, winds, and directed gas flows from AGN. Combining hydrodynamical simulations with ACT and Planck observations will directly test whether current feedback prescriptions reproduce observed SZ signals.

The methodology uses the moving-mesh code Arepo to perform many zoom-in cosmological simulations to match observed galaxy distribution, with emphasis on generating synthetic SZ maps that reproduce observational systematics for rigorous model-data comparisons. The student will use physically-motivated models that resolve the jet propagation and calculate the jet powers based on inferred AGN accretion disc. By exploring extended AGN feedback parameter space, this investigation aims to identify models satisfying both galaxy-scale observables and cosmological clustering statistics across scales.

Supervisory team: Vid Irsic, Martin Bourne, Laura Keating, Chiaki Kobayashi

State-of-the-art cosmological simulations have achieved remarkable success in reproducing observations of galaxy formation in the local Universe. However, these simulations rely heavily on sub-grid models to represent complex physical processes within galaxies — such as feedback from supernovae and black holes — that inject energy and material into the surrounding circumgalactic and intergalactic medium, influencing subsequent star formation.

While these feedback models are typically calibrated to match present-day observables (e.g. the galaxy stellar mass function or stellar-to-gas mass relations), their impact during the early phases of galaxy evolution remains poorly understood. This is largely due to the limited statistical knowledge of galaxy populations prior to the peak of cosmic star formation.

This project will use the intergalactic medium (IGM) as an indirect probe to study how galaxies deposit energy into their environment at high redshift. The student will conduct controlled cosmological simulations using the AREPO code, systematically varying feedback prescriptions targeted at early epochs (z > 2) while maintaining consistency with local observables. By comparing the resulting IGM signatures with observations, the project aims to place the first constraints on the evolution of galactic and black hole feedback over cosmic time.

The outcomes will provide key insights into the physical processes driving early galaxy formation, bridging the gap between local galaxy observations and high-redshift measurements from facilities such as James Webb Space Telescope (JWST), and informing the next generation of large-scale galaxy surveys.

Supervisory team: Jan Forbrich, Martin Krause, Souradeep Bhattacharya

Star formation, the process by which gas and dust give rise to new stars, is studied both within our own Milky Way and in nearby galaxies. Traditionally, these two approaches have been separated: Galactic studies provide detailed insight into individual molecular clouds and young stars, while extragalactic work explores star formation on much larger scales across entire galaxies. This division has made it challenging to connect our detailed understanding of local processes, which are unlikely to be representative, with the broader trends seen elsewhere.

Recent advances in observational capabilities now make it possible to bridge this gap. By observing nearby galaxies such as the Andromeda Galaxy (M31) at resolutions comparable to studies within the Milky Way, we can directly compare the physics of star formation across very different environments. In our ongoing large-scale science project, we are conducting such studies using data from world-class facilities including ALMA, NOEMA, the Submillimeter Array, the VLA, and optical spectroscopy from the MMT. We have recently developed a novel analysis method - differential virial analysis - to probe the internal structure of molecular clouds and the initial conditions for star formation (Lada, Forbrich, Krumholz, & Keto 2025; Krumholz, Lada, & Forbrich 2025).

You will use state-of-the-art millimeter interferometry and optical integral field spectroscopy to extend this work to molecular clouds across a wider range of galactic environments. The starting point will be the famous Sculptor Pinwheel Galaxy NGC 300, leveraging substantial ALMA, Herschel, and MUSE data, to compare molecular clouds in this nearby southern-hemisphere spiral galaxy with those in the Andromeda Galaxy, moving toward lower metallicities. In a second step, we will apply similar analysis to local Galactic clouds to put both sets of observed clouds on an equal footing.

The goal is to understand how the initial conditions of star formation vary on cloud scales and to connect these extragalactic results to what we know from detailed Galactic studies, thereby bridging the persistent gap between extragalactic and Galactic star formation science.

Supervisory Team: Pedro Carrilho, Carolyn Devereux, Martin Hardcastle

Recent measurements of cosmological scales at early and late times have been found to disagree on the determination of the expansion rate of the Universe and of the clustering of matter. Additionally, recent probes of the expansion of the Universe, such as the Dark Energy Spectroscopic Instrument (DESI), show a preference for evolving dark energy. These results hint that the standard cosmological model requires updating and may represent the first clues on the true nature of dark matter and dark energy that fill the Universe today. It is a great time to explore these alternative cosmologies, given the richness of new data starting to poor in from surveys of cosmic structure. In particular, the Euclid mission is probing the evolution of structure in the Universe to an unprecedented accuracy, measuring both the clustering of galaxies and the weak lensing generated by dark matter. Using this data, it will test cosmic tensions while probing the physical theories that can explain them, as well as testing modified gravity and the initial state of the Universe.

This project will develop new tools for analysing the data from Euclid within non-standard cosmological models motivated by cosmic tensions. It will use analytical methods, simulations and machine learning tools to accurately and efficiently predict the various effects arising in these alternative cosmologies, particularly accounting for nonlinear structure formation, and the feedback of gas physics. In parallel, the project will explore novel physical theories, including some fundamental aspects of Cosmology. Moreover, it will use advanced data science techniques to analyse the data from multiple cosmological surveys and extract the information about the physics of dark matter and dark energy that could revolutionise our understanding of the Universe. In particular, the project will directly contribute to the work being developed within the Euclid consortium and will give early access to its data and to the generation of its state-of-the art results.

Supervisory Team: Sophie Koudmani, Martin Bourne, Chiaki Kobayashi

This PhD project will explore how the first supermassive black holes (SMBHs) formed and grew in the early Universe: a key mystery now being illuminated by the James Webb Space Telescope (JWST). The student will develop and apply next-generation models of SMBH accretion and feedback within cosmological simulations, building new tools for synthetic JWST observations to enable direct comparisons between theoretical predictions and observations.

The project will employ a newly developed unified accretion disc model implemented in the moving-mesh code AREPO, capable of capturing both radiatively efficient and inefficient accretion regimes. This model will provide highly accurate predictions for the growth rates of infant SMBHs. The student will couple this unified model with leading SMBH seed formation scenarios (including remnants of Population III stars, runaway stellar clusters, and direct gas collapse) to break long-standing degeneracies between SMBH seeding and accretion.

In the next stage, the project will extend the unified model to include super-Eddington accretion and radiative feedback, allowing the exploration of how extreme accretion episodes shape black hole growth and host galaxy evolution. Using this new multi-scale, multi-physics framework, the student will perform high-resolution cosmological zoom-in simulations that resolve scales down to ~0.01 parsec (the scale of the accretion disc) around growing SMBHs.

These simulations will then be used to generate synthetic JWST NIRCam and NIRSpec observations, employing spectral energy distribution (SED) and mock integral field unit (IFU) modelling to create direct theoretical counterparts to ongoing JWST observing programmes. Depending on the student’s interests, the project could further explore primordially seeded black holes and/or extend the synthetic observation tools to other wavelengths and instruments, providing a broad and flexible platform for the efficient scientific exploitation of early-Universe observations.

This project may be offered for 3.5 or 4 years, depending on the availability of funding.

Supervisory Team: Sophie Koudmani, Sugata Kaviraj, Martin Bourne, Vid Irsic

Dwarf galaxies are the smallest building blocks of structure formation in the ΛCDM Universe. They are the most numerous type of galaxy, yet several long-standing “dwarf galaxy anomalies” reveal stark mismatches between theory and observation. As next-generation large-scale surveys push to lower galaxy masses and higher redshifts, further challenges to our theoretical models have emerged, in particular a higher-than-expected fraction of dwarfs have ceased forming stars, and a large sample of dwarf galaxies hosting active black holes has been uncovered.

This has prompted a paradigm shift: black holes were previously neglected in dwarf galaxy models, and self-quenching was presumed inefficient for low-mass systems. The student will develop and analyse a new generation of high-resolution mid-volume cosmological simulations with the moving-mesh code AREPO, incorporating physically motivated models for AGN activity in dwarf galaxies, stellar feedback, and tidal disruption events.

The project’s central goal is to pioneer a realistic numerical framework for exploring black hole feedback, star formation, and morphological transformations in the low-mass regime. The student will compare simulated galaxy populations with deep multi-wavelength datasets, including COSMOS2020, to test how well the model reproduces observed stellar masses, colours and AGN demographics. By tuning the efficiency and variability of accretion and feedback processes, the project will establish a self-consistent “dwarf galaxy laboratory” to create synthetic surveys and make predictions for the Rubin Observatory’s Legacy Survey of Space and Time (LSST) and beyond.

This project may be offered for 3.5 or 4 years, depending on the availability of funding.

Supervisory Team: Ashley Spindler, Gulay Gurkan

Disk-type galaxies have wide and varied morphologies, from grand spiral arms and galactic bars, to rings and flocculent disks. The properties of these structures are influenced by the evolutionary history of the galaxy, and in turn influence the development of their hosts. Bars, for example, drive gas and dust from the galactic disk into the central bulge, triggering intense star formation and feeding the galaxy’s supermassive black hole. But studying the internal properties of these structures across a large sample of galaxies has, until recently, been very difficult. Utilising state-of-the-art AI tools, trained using data from citizen science programs, we can now perform this task at very large scales, producing structural maps of hundreds of thousands of galaxies.

With this data, we can begin to unravel the evolutionary histories of spiral galaxies and answer important questions about their development. Why do some galaxies host bars and others don’t? What causes the shutdown of star formation? How does the pitch angle of spiral arms relate to stellar mass, bulge-to-disk ratio, and other properties? How do ringed galaxies differ from spirals, and are they really the remnants of galactic bars? What is the relationship between disk galaxy structure and active galactic nuclei? There is room in this project to cater to the interests and skill set of the student.

This project will primarily use data from DESI, but opportunities exist to include data from public JWST catalogues such as CEERS and JADES, imaging from the Euclid Space Telescope, and LSST. There will also be opportunities to work with the Galaxy Zoo research team on new citizen science projects related to this project.

Supervisory Team: Sugata Kaviraj, Aaron Watkins, Darshan Kakkad

Our current understanding of the Universe is dominated by bright objects (e.g. massive galaxies like the Milky Way), because such systems are brighter than the detection thresholds of past large observational surveys (e.g. the SDSS). However, the majority of stars in the Universe actually reside in the faint or ‘low surface brightness’ regime, i.e. in objects and structures that are much fainter than the detection limits of past surveys. This regime contains all dwarf (low-mass) galaxies which dominate the galaxy number density, making them critical to our understanding of galaxy evolution. It also includes faint tidal debris created by galaxy mergers, which are key to understanding how gravity, the predominant force in the Universe, shapes galaxy evolution over cosmic time. Put simply, a complete understanding of how the Universe evolves is not possible without a detailed comprehension of the low surface brightness regime.

Astrophysics is currently entering a revolutionary era of new surveys, which not only have large areas but are also incredibly deep. In particular, the Legacy Survey of Space and Time (LSST) and the Subaru Strategic Program from the Hyper Suprime-Cam telescope, are poised to transform our understanding of the Universe, by providing images that are more than 100 times deeper than those from previous surveys. These images will enable us to perform detailed studies of the low surface brightness Universe for the first time.

This project will combine state-of-the-art data from these surveys with in-house cosmological simulations (e.g. NewHorizon) and advanced machine-learning techniques we have developed (e.g. Martin et al. 2020), to perform the first statistical studies of the low-surface-brightness Universe. The project will map the properties of dwarf galaxies in unprecedented detail, over at least half the lifetime of the Universe and quantify the role of key processes like galaxy merging in driving star-formation, black-hole growth and morphological transformation in galaxies over cosmic time.

The student will collaborate closely (through visits and conference trips) with colleagues in Paris, Oxford and a worldwide network of scientists within the international LSST project (in which our team members hold several leadership roles). The project will give the student an excellent skillset in astronomical observation, theory and machine-learning that is well-aligned with this new era of Big Data astronomy.

Supervisory Team: Darshan Kakkad, Sugata Kaviraj, Chiaki Kobayashi, Dan Smith

Supermassive black holes (SMBHs) residing at the centres of most galaxies play a pivotal role in regulating star formation within their hosts. This process, known as Active Galactic Nucleus (AGN) feedback, operates via powerful winds and outflows launched from the black hole’s accretion disk and/or collimated jets observed in the radio. These winds can either expel the cold molecular gas that fuels star formation or heat it sufficiently to prevent stars from forming. AGN feedback has become a key ingredient in several cosmological hydrodynamical simulations that model galaxy formation and evolution.

Despite decades of observations of galaxies hosting AGN, the physical details of this feedback process remain poorly understood. We are still far from establishing a comprehensive picture of how black holes influence their host galaxies across the broader galaxy population. This is particularly true for galaxies hosting low-mass black holes or black holes with low mass accretion rates, which are thought to have been the dominant population throughout much of cosmic history.

In the 2020s and 2030s, large-scale statistical spectroscopic surveys of AGN host galaxies will provide unprecedented opportunities to explore these questions. This PhD project will utilise state-of-the-art spectroscopic data from the 4MOST CHANGES community survey (Bauer et al. 2023). 4MOST is the largest spectroscopic facility in the Southern Hemisphere and you will become part of a diverse international collaboration working to detect fast accretion-disk winds and to characterise the interstellar medium of AGN host galaxies (stellar age, metallicity) and their connection to black hole mass and luminosity. You will also integrate these observations with data from publicly available spectroscopic surveys to build a more complete statistical framework.

Beyond its scientific goals, this project also offers extensive opportunities to develop interdisciplinary expertise in data science, data management, and machine learning, given the statistical nature of the datasets.

Supervisory Team: Martin Hardcastle, Jonathon Pierce, Bonny Barkus

Radio galaxies are active galaxies (AGN) in which powerful jets are ejected from close to the central supermassive black hole and propagate through their host galaxy and the surrounding group or cluster medium. The impact of the jets is thought to have a profound effect on the evolution of the most massive galaxies throughout cosmic time.

It is crucial to test this model by finding the radio galaxies and quantifying the energy that they put into different environments and at different times. Radio galaxies are inherently rare objects, as they include the most powerful AGN at any given epoch, and so the problem with studying radio galaxy evolution has always been the need to combine high-quality wide-area radio surveys with the deep optical surveys needed to find distant galaxies. Existing work with wide area surveys falls short of probing the early universe in which we expect to be able to see significant evolution of the radio AGN population (e.g. Hardcastle et al 2025).

The combination of LOFAR and Euclid is about to provide a step change in our ability to do this work. LOFAR has carried out the deepest ever wide-area survey over the Northern sky, a project in which we have been heavily involved since it began, and from 2027 this will start to be supplemented by data from the high-resolution iLoTSS survey using the upgrade LOFAR 2.0. Euclid is carrying out a wide-area optical/infrared sky survey which will be significantly deeper than any previous survey of the same kind, and will benefit from the high resolution available from space; we are leading work on the combination of Euclid and radio observations within the Euclid and LOFAR consortia. By combining these datasets we will get the best ever view of the radio AGN population, extending well into the ‘cosmic noon’ epoch where galaxies are at their most active. We will for the first time be able to study how radio galaxies affect their environments as a function of cosmic time back to this high redshift, and to compare our observations to the predictions of cosmological simulations. This work will support developments towards early survey science with the Square Kilometer Array (SKA) which we expect to be coming on line within the timeframe of the PhD project and which will give comparable data to LOFAR in the Southern hemisphere.

Supervisory Team: Dom Walton, Will Alston

Accretion onto compact objects powers some of the most luminous and extreme phenomena in the universe. Accreting supermassive black holes ultimately power all of the different populations of active galactic nuclei (AGN), while stellar remnant black holes and neutron stars power luminous X-ray binary systems (XRBs) that are scattered throughout all major galaxies. This accretion process also drives powerful outflows (winds, jets) that allow these compact sources to impact their surroundings, and are responsible for driving the 'feedback' processes that dictate the observed co-evolution of supermassive black holes and their host galaxies. Understanding this accretion process (and its by-products) is therefore of critical importance. In particular, there are still major questions to be answered regarding how supermassive black holes came to be as massive as they are today (and, in the most extreme cases, how they were able to rapidly do so while the universe was still in its relative infancy).

Two potential projects are available, on black hole spin and on ultraluminous X-ray sources, both of which will primarily involve analysis of both new and archival X-ray observations from e.g. the XMM-Newton, Swift, Chandra and NuSTAR observatories, including spectroscopic and time-domain analyses. In addition to the immediate scientific progress, both will also serve as key preparation for the Athena X-ray observator (ESA’s next flagship-class space telescope) and potentially also the AXIS X-ray observatory (a Probe-class mission under consideration by NASA), as well as offering connections with the gravitational wave community.

Black Hole Spin: in astrophysics black holes are expected to be fully defined by just two numbers, their mass and their spin (or angular momentum). Information on the growth history of SMBHs is imprinted on their spin distribution, and so SMBH spin measurements are of particular importance for understanding this process, and in turn galaxy evolution (which is inextricably linked to SMBH growth). Such measurements are possible via detailed X-ray spectral/timing analyses of accreting black holes, and the main aim of this project is to continue growing the sample of SMBH spin measurements in order to populate the SMBH spin-mass plane that will eventually allow us to test SMBH growth models. In addition to measuring the black hole spin parameter, the same techniques can be used to probe the properties of the innermost accretion flows in AGN, furthering our understanding of the complex physics of accretion at play in these systems. Furthermore, the same techniques can be used to measure spin in black hole XRBs, offering a means to compare the XRB population with the black holes seen merging via gravitational waves.

Ultraluminous X-ray Sources: these are the most extreme XRBs and are now understood to be the best local examples of accretion above the Eddington limit, which may be required to grow the SMBHs now being seen in the early universe. ULXs were themselves assumed to be black holes for a long time, but remarkably we now know that some ULXs are powered by wildly super-Eddington neutron stars! Only a handful of these neutron star ULXs are currently known, but there is speculation they may make a significant contribution to the broader ULX population. In fact, we are still hunting for the first confirmed black hole ULX, although there is again speculation that such systems exist as evolutionary precursors to the black hole mergers seen via gravitational waves. The primary goal here is to further our understanding of the ULX population, studying the known ULX pulsars to understand how they are able to accrete at such extreme rates, searching for new ULX pulsars, and also for the first black hole ULX.

Supervisory team: Emma Curtis-Lake, Darshan Kakkad, Chiaki Kobayashi