Mapping the Uncharted Horizons of the Milky Way

Abstract

The most distant stars around the Milky Way encode a fossil record of our Galaxy's assembly history, and trace the large-scale distribution of its dark matter. This thesis presents results from our all-sky spectroscopic surveys of stars in the Galactic outskirts. We unveil enormous stellar structures imprinted by the Milky Way's last major merger, and illustrate how this merger may have reshaped our own Galaxy's evolution. We use spectroscopy to discover the faintest known disrupting dwarf galaxy, and to uncover the long-sought stellar counterpart to the Magellanic Stream. Finally, we derive the most comprehensive measurements of the Galaxy's global dynamical response to the infalling Large Magellanic Cloud, providing an independent window into the dark matter distribution in both galaxies. Looking ahead, we lay the foundation for the fifth-generation Sloan Digital Sky Survey and the Via Survey to expand new frontiers, from the evolution of the Milky Way to the nature of dark matter.