Testing Galaxy Formation Models with Large-scale Surveys of the Milky Way Stellar Halo

While the vast majority of the light from our galaxy comes from the Galactic disk, the vast majority of the mass of the Milky Way (MW) is in its dark matter halo. Because we cannot directly observe the MW's dark matter halo, we must use luminous tracer populations (i.e., stars) to study the mass distribution indirectly. Fortunately, there are stars strewn throughout the MW's dark matter halo. We believe the MW built up its halo of dark matter over cosmic time by consuming smaller dwarf galaxies; the remnants of these dwarf galaxies make up the MW's stellar halo. Halo stars can therefore be used both to constrain the dark matter distribution of the MW as well as inform us about the dwarf galaxies in which they formed. I will present my ongoing theoretical and observational work using halo stars to map the dark matter distribution and disequilibrium in the MW, as well as study the faint, low-mass galaxies that were consumed by the MW during its formation. I will discuss the crucial roles of current and upcoming large-scale surveys of the MW halo (such as the Rubin Observatory Legacy Survey of Space and Time) for addressing fundamental questions in galaxy formation.

Bio: Prof. Cunningham’s research uses observations and simulations of the Milky Way halo to address questions that are fundamental to understanding galaxies and dark matter. Halo stars are luminous tracers of the MW’s DM halo and mass assembly, and are relics of disrupted dwarf galaxies that did not survive until present day. The properties of stellar halos are determined by the nature of dark matter as well as the conditions of galaxy formation in the early universe. Professor Cunningham’s research program has two main branches: 1) mapping the DM distribution and disequilibrium in the MW and 2) using halo stars to study the faint, low-mass galaxies that were consumed by the MW during its formation. (Credit: https://www.bu.edu/astronomy/profile/emily-cunningham/)