Dynamics All the Way Down: The Satellites, Streams, and Stellar Halo of the Milky Way in the Gaia Era

Abstract

The release of high-precision astrometric data from the Gaia space mission has revolutionized studies of the Milky Way’s halo substructures over the past few years. In this dissertation, I use this data to model the dynamics of Milky Way satellite galaxies, globular clusters, stellar streams, and the stellar halo, often by incorporating comparisons to cosmological simulations that include galaxy formation. I find that the Milky Way satellite galaxies have tangentially dominated motions, a kinematic signature consistent with the central galaxy disrupting radial orbits that pass nearby. Using updated catalogs of globular cluster phase-space measurements and new stellar stream discoveries, I show that these substructures are not aligned with the Milky Way’s plane of satellite galaxies, suggesting this unusual orbital configuration in ΛCDM is not a long-lived structure or the result of a recent accretion event. I additionally report a new dynamical association between the globular cluster NGC 3201 and the Gjöll stellar stream, which is confirmed using spectroscopic follow-up to obtain radial velocities and chemical abundance information. Finally, I describe how we can develop simulation and modeling infrastructure to properly leverage observations from upcoming facilities in the next generation of Local Group dynamical studies.