The most dark-matter-dominated galaxies: Predicted gamma-ray signals from the faintest milky way dwarfs

We use kinematic data from three new nearby, extremely low luminosity MilkyWay dwarf galaxies (UrsaMajor II, Willman 1, and Coma Berenices) to constrain the properties of their dark matter halos, and from these we make predictions for the gamma-ray flux from annihilation of dark matter particles in these halos. We show that these similar to 10(3)L(circle dot) dwarfs are the most dark-matter-dominated galaxies known, with total masses within 100 pc that are in excess of 10(6) M-circle dot. Coupled with their relative proximity, their large masses imply that they should have mean gamma-ray fluxes that are comparable to or greater than those of any other known satellite galaxy of the Milky Way. Our results are robust to both variations of the inner slope of the density profile and the effect of tidal interactions. The fluxes could be boosted by up to 2 orders of magnitude if we include the density enhancements caused by surviving dark matter substructure.