Galaxies are born and evolve within halos of dark matter. The Cold Dark Matter paradigm predicts that large galaxies such as the Milky Way contain a wealth of substructure around the main dark matter halo. During the past decade, astronomical surveys have enabled us to study the small-scale distribution of dark matter in unprecedented detail through the discovery of extremely low luminosity galaxies orbiting the Milky Way. These ultra-faint galaxies are among the most dark matter dominated objects known, but can only be detected in the local cosmic neighborhood because they have so few stars. The census of Milky Way satellite galaxies has nearly doubled in the past six months, thanks in large part to early data from the Dark Energy Survey (DES), a five-year campaign to map 300 million galaxies over one-eighth of the full sky. I will describe these recent discoveries and explain how the emergent population of ultra-faint galaxies can be used to explore the particle nature of dark matter.

Argonne Physics Division Seminar Schedule