H I IN LOCAL GROUP DWARF GALAXIES AND STRIPPING BY THE GALACTIC HALO

We examine the H I content and environment of all of the Local Group dwarf galaxies (M-tot < 10(10) M-circle dot), including the numerous newly discovered satellites of the Milky Way and M31. All of the new dwarfs, with the exception of Leo T, have no detected H I. The majority of dwarf galaxies within similar to 270 kpc of the Milky Way or Andromeda are undetected in H I (< 10(4) M-circle dot for Milky Way dwarfs), while those further than similar to 270 kpc are predominantly detected with masses similar to 10(5) to 10(8) M-circle dot. Analytical ram-pressure arguments combined with velocities obtained via proper motion studies allow for an estimate of the halo density of the Milky Way at several distances. This halo density is constrained to be greater than 2x 10(-4)-3 x 10(-4) cm(-3) out to distances of at least 70 kpc. This is broadly consistent with theoretical models of the diffuse gas in a Milky Way-like halo and is consistent with this component hosting a large fraction of a galaxy's baryons. Accounting for completeness in the dwarf galaxy count, gasless dwarf galaxies could have provided at most 2.1 x 10(8) M-circle dot of H I gas to the Milky Way, which suggests that most of our Galaxy's star formation fuel does not come from accreted small satellites in the current era.