Astrophysics Colloquium: The Milky Way In Surveys Large and Small

Abstract: We observe our Milky Way Galaxy by observing its stars.  That gives us the challenge and opportunity to learn how how the stars in our Galaxy's halo, and the dark matter subhalos that hosted them, were assembled as our Galaxy grew.  We can also learn how the motions of individual stars collectively create our Galaxy's large-scale response to gravitational interactions in the present day.   I will describe an investigation of how a small survey can illuminate the big-picture trends in the formation of the Milky Way.   I will then introduce the  Dark Energy Spectroscopic Instrument (DESI) Milky Way Survey, and some recent results showing how the motions of stars in the Galactic anticenter point to large scale perturbations of the disk of our Galaxy, likely in response to Sagittarius as it is accreted by the Milky Way.