HI in Local Group Dwarf Galaxies and Stripping by the Galactic Halo

Understand

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.