Astrolunch: Josh Simon (Carnegie)

Tue, 03/03/2020 - 12:30 to 13:30

A 4D view of the Local Group
The dwarf galaxies around the Milky Way are extremely valuable laboratories for studying the nature of dark matter, the threshold for galaxy formation, and chemical evolution in the early universe. After reviewing the revolution in our understanding of the Milky Way's satellite population that has resulted from recent wide-field imaging surveys, I will discuss new proper motion measurements of nearby dwarfs using the Gaia satellite. Gaia has made it possible to instantly determine the proper motions of galaxies out to distances beyond 100 kpc. The velocities for dwarfs within this distance are generally measured to better than 50 km/s, even when only a handful of known member stars are bright enough for Gaia measurements. Based on the resulting 3D space motions for each dwarf I compute their orbits around the Milky Way and extrapolate backward in time. I use these 3D velocities to identify satellites of the Magellanic Clouds, quantify the effect of tides on each dwarf galaxy, and investigate the quenching of star formation in the smallest dwarfs.