Speaker: Keith Bechtol, UW - Madison, Wisconsin IceCube Particle Astrophysics Center
Abstract: The population of satellite galaxies orbiting the Milky Way includes the most ancient, most chemically pristine, and most dark matter dominated galaxies in the known universe. These objects have reshaped how we define a “galaxy” and provide a unique testing ground both for galaxy formation models and the cold dark matter paradigm. The current census of roughly thirty galaxies surrounding the Milky Way is almost certainly incomplete. Ongoing and near-future wide-field optical imaging surveys are anticipated to find hundreds of ultra-faint Milky Way companions at lower luminosities, greater distances, and in less explored regions of the sky. Over twenty new low-luminosity stellar systems were discovered in 2015, and several of these have now been dynamically and/or chemically confirmed as galaxies. I will place these recent results in context and consider what the emergent population of Milky Way satellites can teach us about the first stars and galaxies, as well as the particle nature of dark matter. Finally, I will discuss the exciting prospects for near-field cosmology in the coming decade.