Institute for Astronomy
Institute for Astronomy
Contact us

Galaxy Formation & Evolution PhD Projects

Research projects on offer in our Galaxy Formation & Evolution group:

An unbiased view of galaxy evolution across cosmic time from ultra-deep radio imaging

Prof Philip Best and Dr Catherine Hale

A fundamental limit to our understanding of galaxy evolution is the role of dust in obscuring the light from star-forming galaxies. Radio-frequency emission passes through dust and therefore offers an unbiased tracer of star-formation across cosmic time. State-of-the-art radio telescopes such as the LOw Frequency ARray (LOFAR) now have the sensitivity to detect ‘normal’ star-forming galaxies across cosmic time, and also offer the high angular resolution to be able to resolve the galaxies. This is crucial to obtain the morphology of the star-formation, and hence address critical questions around the way in which mass builds up in galaxies. It also allows us to separate the emission from star-formation from that of ‘radio-quiet’ AGN (i.e., AGN which are much brighter at other wavelengths compared to their radio emission), which themselves trace the evolution of black hole growth across cosmic time.

Edinburgh has led the ‘LoTSS Deep Fields’ project, a deep degree-scale radio imaging survey, and over the few years will co-lead the LOFAR Ultra Deep Observation (LUDO): the deepest wide-area radio observation ever undertaken. LUDO is co-located with a deep multi-band optical/IR imaging survey carried out by the Euclid Space Telescope, and will facilitate a wealth of opportunities to study star-forming galaxies and radio-quiet AGN. The proposed project is to lead exploitation of the LoTSS Deep Fields and LUDO, in particular for studies of star formation over large periods of cosmic time. There is flexibility in the precise programme of work, depending on the interests of the student. The student will work closely within the international LOFAR surveys collaboration and gain considerable experience with high resolution radio data and studying galaxy evolution using a combination of multi-wavelength data; this will position them well for exploiting the Square Kilometre Array in the 2030s.

Understanding chemical enrichment and the nature of massive stars at early cosmic epochs with JWST

Dr Fergus Cullen

The James Webb Space Telescope (JWST) has revolutionized our ability to study the early Universe. With galaxies having been discovered up to z=14 (just 300 Myr after the Big Bang), we are now in a position to investigate the earliest stages of their assembly. One key observational probe of galaxy formation is the level of chemical enrichment. Since the Big Bang only lasted long enough to fuse hydrogen into helium (plus small amounts of lithium), all other elements were produced in the interior of successive generations of massive stars. The chemical enrichment history of galaxies therefore contains crucial information about their past history of star formation and stellar mass build-up.

Moreover, by tracking the enrichment of different elements, we can gain important insight into the nature of the massive stellar populations forming at the earliest epochs. For example, one key puzzling result from early JWST observations has been the clear signature of nitrogen excess observed in some galaxies at very high redshifts. A definitive explanation for this enrichment has not yet been reached, but some explanations include exotic populations of very massive stars, or changes to the stellar initial mass function (IMF) in pristine galaxies at early times. The discovery of ultra-hot gas in the most metal-poor galaxy yet discovered (Cullen et al. 2025) has also suggested that new extreme stellar populations – not yet fully understood – may exist in some galaxies at the highest redshifts. Finally, a signature of enhanced carbon enrichment in one lensed galaxy at z=6 has been posited as evidence for the long-sought-after 'first generation' of star formation.

Despite the past three years of progress, many open questions remain including: (i) what are the levels of chemical enrichment in galaxies at z > 8? (ii) what are the primary modes of carbon and nitrogen enrichment and what is the root cause of the enhanced enrichment of these elements? (iii) is there solid evidence for exotic stellar populations or evidence for a top-heavy IMF in metal-poor galaxies at early epochs? The aim of this PhD is to characterise the chemical evolution of galaxies at the earliest cosmic epochs and tackle these open questions using deep JWST spectroscopy. The project will utilise archival JWST data from major surveys including our in-house EXCELS dataset and other publicly available data. By measuring critical abundance ratios (e.g., O/H, N/O, C/O), analysing stellar continuum features, and examining signatures of the ionising photon production efficiency of massive stars, this research will provide new insights into the enrichment histories (and pathways) as well as the nature of massive stars in the first galaxies.

Charting the growth of supermassive black holes in the young Universe

Prof James Dunlop, Prof Ross McLure, and Dr Derek McLeod

It has been known for several years now that the existence of bright quasars at redshifts as high as z~7 means that billion-solar-mass black holes were in place less than 1 Gyr after the Big Bang. The route by which such supermassive black holes came to be has been much debated by theoreticians, but such extreme objects are very rare, and until now the prevalence of more modest mass black holes at early times (potentially including the ancestors of those that power quasars) was essentially unknown.

In the last two years however, early data from the James Webb Space Telescope (JWST) has indicated that supermassive black holes may be much more common in the young Universe than previously supposed. The evidence comes from the spectroscopic discovery of broad emission lines in early galaxies (indicative of active galactic nuclei: AGN) and from the discovery of an apparently new population of very compact, red objects (termed "little red dots") which may be dust obscured AGN.

However, at present the situation is very confused. Many early galaxies are known to be compact, and broad emission lines can result from the outflows produced by intense star-formation activity. At high redshifts it is also a major challenge to reliably separate the unresolved light from an active black hole from the starlight in its host galaxy, even with the exquisite resolution of JWST.

This observational project aims to sort out this situation through a multi-pronged approach. Existing and imminent JWST NIRCam, MIRI and NIRSpec data will be used to clarify which early galaxies host AGN, and to properly determine their black-hole and host-galaxy masses. This will be achieved by using MIRI to search for warm (AGN-heated) dust, using NIRSpec to obtain spectroscopic estimates of black-hole mass, and by carefully analysing the highest resolution NIRCam data to better constrain the relative contributions of nuclear and extended light in high-redshift galaxies. Deep stacking of X-ray data and of the growing wealth of new radio data may also be explored, to provide a more complete multi-frequency perspective.

Radio sources in the cosmic web: Studying the impact of environment on AGN and star formation activity using new spectroscopic surveys

Dr Catherine Hale, Dr Kenneth Duncan, and Prof Philip Best

Spectroscopy is crucial in the study of galaxies within the cosmic web - providing the accurate redshift information which allows sources to be definitively placed within the large-scale structure of the Universe (the cosmic web) and, thus, accurately study the local environment of such objects. Environment plays a role in the evolution of galaxies over cosmic time, with galaxies both impacting, and being impacted by, their local environment, especially when feedback plays a role from supermassive black holes and star formation. However, the detailed interplay between galaxies and their environment remains poorly understood. Extragalactic radio surveys directly trace both powerful, accreting supermassive black holes (known as AGN) and galaxies which have undergone a process of star-formation (known as SFG) – and thus the two key processes which, combined with environment, are important for driving galaxy evolution. In this project, we will use a combination of some of the deepest radio survey data (from telescopes such as from LOFAR and MeerKAT) in combination with new large-scale spectroscopic surveys (from telescopes such as WEAVE and 4MOST) to place radio sources in the cosmic web and study the impact of environment on the evolution of radio sources and sources in their local environment. This research will determine how the properties (e.g. masses, SFR, AGN activity, luminosity functions) of radio detected galaxies vary as a function of physical source properties and their environments. The project can continue to take a number of different research avenues, depending on the interests of the student.

The project will allow involve working and gaining experience in international collaborations working with a combination of radio, multiwavelength and spectroscopic data.

Illuminating the Universe with the First Galaxies and the James Webb Space Telescope

Dr Laura Keating

As the first stars and galaxies formed, the ultraviolet light they emitted ionized and heated the gas surrounding them, in a process known as reionization. Understanding the process of reionization is crucial for determining how and when the first galaxies in the Universe formed. Bright galaxies have been detected when the Universe was only a few hundred million years old, but these are expected to be rare, biased objects. “Normal” galaxies in the early Universe lie below the threshold for direct detection with powerful telescopes but they can still emit ionizing photons. The process of reionization is therefore sensitive to all galaxies, not just the bright, detectable ones. A complete understanding of reionization can give an indirect view of the faintest first galaxies and reveal the physics driving galaxy formation in the early Universe. However, there are still many unknowns about reionization, including exactly when it took place and the properties of the sources that provided the ionizing photons. With the fantastic new observations from the James Webb Space Telescope, we can now start to answer these open questions.

In this PhD project, you will interpret the new James Webb observations to reveal the reionization history of the Universe and obtain a unique view of the first galaxies. Depending on the interests of the student, the project can take different directions, from a focus on analysing the observational data, to performing new cosmological simulations of the reionization process. The project will offer the opportunity to collaborate with other researchers based in Edinburgh and at other institutions around the world.

Machine Learning Galaxy Formation

Prof Sadegh Khochfar

Video: Machine Learning Galaxy Formation
IfA PhD Projects

In this project, we want to develop new machine-learning algorithms to investigate galaxy formation in the Universe. The algorithms will be applied to numerical simulations of galaxy formation in a first step and then used on observations. The idea is to break degeneracies between simulations and models used in the community and to identify the most important astrophysical drivers of galaxy formation. The student would work with data sets available in the group and from international collaborations.

Properties of primeval and reionization-era galaxies with JWST

Dr Derek McLeod, Prof Ross McLure, and Prof James Dunlop 

With the advent of the James Webb Space Telescope (JWST) and its mid-infrared capabilities, we have made remarkable progress in the study of cosmic star formation history at z > 9, with evidence of significant star formation taking place even ~400 million years after the Big Bang, beyond the observational horizon of the Hubble Space Telescope (HST). However, there has been limited recent progress in three key areas:

  1. Our understanding of the demographics of the UV-brightest galaxies in the epoch of reionization (i.e., z ~ 6-11) beyond what has been achieved through wide-area (but lower resolution) ground-based works combining the VISTA and Subaru telescopes, or HST+JWST legacy fields covering modest search areas of ~400 sq. arcmin.
  2. Our understanding of the very faintest galaxies in the epoch of reionization. The current state-of-the-art z = 6-7 UV luminosity function (UV LF) determinations are still from the pre-JWST era, and there have been few studies probing statistically significant samples of fainter (MUV > -18) galaxies at z > 8 with JWST to date.
  3. Our first glimpse of the first galaxies is hitherto limited to spectroscopic confirmations at z ~ 14, with only some tentative photometric candidates at higher redshift.

This observational PhD project presents an excellent opportunity to address these questions. From the first four cycles of JWST operations, there is approximately 1 sq. degree of public JWST NIRCam imaging available, including from numerous, wider-area legacy surveys (e.g., PRIMER, COSMOS-Web/3D), ultra deep fields (JADES/JOF, NGDEEP) and cluster surveys with the potential to investigate intrinsically faint galaxies lensed by foreground massive galaxy clusters (GLIMPSE, CANUCS, VENUS). This project aims to leverage an unprecedented data set combining a large suite of this publicly available NIRCam imaging, with which we can:

  1. Investigate the demographics and properties of UV-bright high-redshift galaxies: much focus has been placed upon the discovery of an abundance of 'blue monster' (MUV < -20) galaxies at z > 10. This abundance could arise due to the emergence of dust-free stellar populations at z > 10, and/or 'bursty' star-formation histories/UV variability.
  2. Characterize the properties of 'typical' galaxies in the reionization era, i.e., the fainter galaxy population (MUV > -19) that represent the bulk of the galaxy population, and are the primary agents of reionization.
  3. Constrain the onset of galaxy formation (the so-called 'Cosmic Dawn'), by investigating the cosmic history of star-formation out to the very highest redshifts z > 15.

The PhD student will also have the opportunity to be involved in a number of JWST-based projects and collaborations within the extragalactic group at Edinburgh, as well as leading proposals for follow-up in future JWST observing Cycles.

Understanding Galaxy Quenching at Cosmic Noon with JWST and MOONS

Prof Ross McLure, Dr Adam Carnall, and Dr Derek McLeod

Over the last four years, the unprecedented sensitivity of the James Webb Space Telescope (JWST) has transformed our understanding of galaxy evolution at high redshifts. We now know that galaxy formation was already well-established by z=14 (only 300 Myr post-Big Bang), chemically mature galaxies existed by z=7, and full-scale quenching of star formation was underway by z=5. Furthermore, at lower redshifts (z<3), JWST has revealed that the population of quiescent or "quenched" galaxies is bimodal. Quenched galaxies above and below a stellar-mass threshold of log M* = 10 display very different morphologies and star-formation histories, consistent with separate populations following distinct evolutionary pathways. This project focuses on better understanding this apparent dichotomy and the relative influence of mass-driven versus environmentally-driven quenching mechanisms.

Complementing JWST's continued ability to study low-mass galaxies at high redshift, the timing of this project is ideally suited to exploit the revolution in ground-based spectroscopy provided by the MOONRISE survey. Starting in late 2026, MOONRISE will utilize the MOONS optical-NIR spectrograph on the VLT to deliver spectra for over 10,000 quiescent galaxies and 100,000+ star-forming galaxies across a survey area of 6-7 square degrees. MOONRISE aims to provide the statistical power and data quality necessary for detailed spectroscopic insights into galaxy quenching, including spectroscopic measurements of galaxy age, star-formation rate, and metallicity for high-mass galaxies during the crucial "cosmic noon" period at 1<z<2.

By interpreting the combined results from JWST and MOONRISE within the context of the latest generation of hydrodynamical simulations, the ultimate goal of this project is to clarify our understanding of star-formation quenching and the evolutionary pathway of quiescent galaxies over the first half of the Universe’s history.

Under the Active Galactic Nuclei projects, see also:

Under the Computational Astrophysics projects, see also:

This article was published on