HI in Local Group Dwarf Galaxies and Stripping by the Galactic Halo
  We examine the HI content and environment of all of the Local Group dwarf
galaxies (M_tot < 10^10 M_solar), 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 HI. The majority of dwarf galaxies within ~270 kpc
of the Milky Way or Andromeda are undetected in HI (< 10^5 M_solar for Milky
Way dwarfs), while those further than ~270 kpc are predominantly detected with
masses ~10^5 to 10^8 M_solar. 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 2-3 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,
gas-less dwarf galaxies could have provided at most 2.1 x 10^8 M_solar of HI
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.
