UCL Astrophysics Group


PhD Projects: Extragalactic Astrophysics

Gas in galaxies as a crucial link between theory and observation

Gas plays a crucial role in the lives of galaxies. It is the raw fuel for new star formation, but it is also heated and sometimes expelled from galaxies by the massive stars that it has just brought to life. Increasingly powerful observations allow us to trace gas in and around galaxies, piecing together clues to their history in a way that is highly complementary to observing the stellar populations alone. This project will explore new ways to constrain the physics of galaxy formation by using our growing understanding of gas in the Universe.  It is a rare opportunity to work with both simulations and observations. Depending on your preference, there is an opportunity to work either primarily with simulations from the GMGalaxies team (led by Andrew Pontzen), or to work primarily with an observational team (led by Amelie Saintonge). Either way, you will interact with both groups.

Contact: Prof Amelie Saintonge (a.saintonge AT ucl.ac.uk) and Prof Andrew Pontzen  (a.pontzen AT ucl.ac.uk)


Exploring the relationship between the early Universe and today’s galaxies

We know that the observable properties of galaxies – their colours and shapes, for example – depend sensitively on their histories, which in turn are determined by inflationary density perturbations in the very early Universe.  There is an opportunity to join the GMGalaxies team (https://gmgalaxies.org) to examine these fundamental links using a unique set of numerical tools. We pioneered “genetic modification” – which involves generating multiple, slightly different sets of early-Universe conditions from which a given galaxy will emerge. As each version of the Universe is evolved in its own computer simulation, the initial differences lead to contrasting evolutions; for instance, the galaxy might be formed earlier or later in the Universe's history, or undergo a different number of mergers with other galaxies. We study these variations and how they impact on the observed galaxy population. There are a broad range of available projects within this programme. There are opportunities to make comparisons to observations, to perform dynamical analyses of simulated galaxies, or to further develop our techniques using statistical and physical models of the very early Universe. 

Contact: Prof Andrew Pontzen  (a.pontzen AT ucl.ac.uk)


Origin and evolution of galactic nuclei in the environments of supermassive black holes

The nuclei of galaxies harbour vital clues to the environments of supermassive black holes that shape their evolution. The discovery and characterisation of the massive black hole at the heart of our own Galaxy was awarded a share of the 2020 Nobel Prize in Physics: this PhD project will study the supermassive black hole at the heart of the nearby Andromeda Galaxy (M31), and its environment.   

The project will utilize high-resolution (0.1” ~ 0.4 pc) observations of the nucleus of M31 obtained with the OSIRIS integral field spectrograph from the W. M. Keck Observatory. This unique data set gives us a full spectrum and line-of-sight dynamical information at every spatial pixel over a 2D (1.5” x 3.5”) field of view. These data yield an unprecedented view into the origin of a precessing eccentric disk of stars that is thought to surround the nuclear black hole. It is already clear that the observed dynamical structure cannot be completely reproduced by current models, and this PhD project will carry out the sophisticated modelling that is required by the new data (including multiple stellar populations and self-gravity of the disk). The project can be extended in different directions, for instance to study data sets on the nuclei of other galaxies, or comparison with our own Milky Way centre, where a Hubble Space Telescope data set of the proper motions of all the stars over the central 2’ (r=1’ = ~2.5 pc) including both the young and old stars is available (from the above-mentioned Nobel prize-winning work). Depending on the interests of the student the work can also be extended in more theoretical directions, such as developing dynamical tests for precession in thick stellar disks. The project will involve collaboration with the group of Prof Jessica Lu at UC Berkeley and prepare the student for a rapidly evolving field: extremely large telescopes (ELTs) are poised to give us access to similar M31-like spatial scales in many other galaxies, and the Nancy Grace Roman Space Telescope will give us unprecedented insights into the heart of our own Galaxy.

Contact: Prof Hiranya Peiris (h.peiris AT ucl.ac.uk)

Related projects are also advertised under Cosmology & Surveys