Institute for Astronomy

Milky Way & Local Group PhD Projects

Research projects on offer in our Milky Way & Local Group Galaxies research group:

A panoramic view of globular cluster systems in the Local Volume

Ruben Sanchez-Janssen and Annette Ferguson

Video: rsj_phd
PhD Projects 2022

Globular clusters (GCs) are old, compact stellar systems orbiting around galaxies of all types. They are thought to form at high redshift out of metal-poor gas at extremely high densities--conditions that were typical in the early Universe. As a result, local studies of GC systems can effectively be used to probe, with a detail and sensitivity unmatched by any observation at high z, both the dominant mode of early star formation and the subsequent assembly process of their host galaxies. This PhD project will produce the first volume-limited census of GC systems around galaxies at distances D < 10 Mpc, for the first time probing the poorly studied regime of low-mass galaxies. The student will use deep optical imaging from the CFIS survey (~5000 deg2) to measure the relative fractions, spatial distributions, and clustering properties of metal-poor and metal-rich GCs in a sample of ~50 nearby galaxies. This data, combined with future WEAVE spectroscopic follow-up to study their kinematics, will allow us to constrain GC formation efficiencies as a function of galaxy mass and environmental density.

Galaxy Archaeology with Asymptotic Giant Branch Stars

Annette Ferguson and Olivia Jones

Thermally-pulsing asymptotic giant branch (TP-AGB) stars are the descendants of low-to-intermediate main-sequence stars with masses in the range of ~1-8 solar masses. Their numbers can therefore be used to measure the star formation histories of galaxies over the last few billion years and their detailed properties constrain the chemical enrichment histories of galaxies as well as their dust production rates. Compared to other resolved stellar population tracers (e.g. main sequence stars, red giant branch stars), AGB stars offer some tremendous advantages. They are extremely luminous at near and mid-IR wavelengths, making them detectable out to ~20 Mpc distances, far beyond the limit of most current resolved population analyses. In addition, the fact that their spectral energy distributions peak at long wavelengths makes them much less susceptible to dust extinction. We are about to enter a golden age for AGB studies in Local Volume galaxies. The launch of JWST in Dec 2021 and Euclid in early 2023 is expected to lead to many breakthroughs in our understanding of this enigmatic phase of stellar evolution and how we can use AGB populations to quantitatively constrain the histories of galaxies.  While JWST will excel in deep pointed observations of individual galaxies at unprecedented spatial resolution, Euclid’s 15,000 sq. degree sky coverage will enable a census of AGB stars in hundreds to thousands of nearby galaxies, including those at the very extremes of the mass distribution — i.e. tiny dwarfs and giant ellipticals.  Jones plays a leading role in JWST GTO programs which are expected to deliver data in 2022 while Ferguson is co-lead of Euclid’s Resolved Stellar Populations Working Group, with first data expected mid-2023.  We seek a PhD student to spearhead the analyses of these and other datasets, with several possible directions depending on the interests of the student.

For further details and information about this project, please download this set of slides:

Probing the Milky Way stellar and dark matter haloes with DESI spectroscopy

Supervisor: Sergey Koposov

 

Over the last 20 years, it became clear that the Milky Way stellar halo is a real treasure trove of information on galaxy formation and evolution because it formed through hierarchical accretion of multiple dwarf galaxies and star clusters onto the Milky Way. The studies of the Galactic stellar halo started to progress rapidly with the arrival of digital sky surveys such as the Sloan Digital Sky Survey and are now experiencing a major revolution thanks to the data from the Gaia satellite.  This satellite provides us with the proper motions and distances of billions of stars. These data have been essential for the recent unexpected discovery that our Milky Way stellar halo is dominated by stars from a massive galaxy labelled Gaia-Enceladus that merged with our Galaxy several billion years ago. Also, Gaia data recently revealed that our galaxy is far from equilibrium and instead is being strongly perturbed by the Magellanic clouds galaxies. While the ongoing Gaia mission is revolutionary, another window into the Milky Way halo is about to open - large spectroscopic surveys that will measure spectra of millions of stars. Measurements from these spectra will provide chemical abundances and radial velocities that will complement the existing datasets, allowing us to create a high-dimensional map of the Galactic halo and all its substructures. One of the earliest major spectroscopic surveys to begin is the DESI spectroscopic survey that just started a regular survey this summer. A student is invited to lead the study of the kinematics and chemistry of distant stars in the Milky Way halo using the data from the DESI survey in combination with data from the Gaia satellite. This work will involve analyses of large datasets, statistical modelling and visualisation. The key research directions will be (i) detecting and characterizing stellar substructures in the Milky Way halo, (ii) measuring the velocity distribution of the smooth halo out to large distances to characterize dark matter mass distribution in the Milky Way. (iii) Discovery of rare objects. Experience with Python is highly recommended. The student will work with Sergey Koposov, his collaborators in Edinburgh and Cambridge, as well as the DESI Milky Way survey working group.