The Gas Content and Stripping of Local Group Dwarf Galaxies
  The gas content of the complete compilation of Local Group dwarf galaxies
(119 within 2 Mpc) is presented using HI survey data. Within the virial radius
of the Milky Way (224 kpc here), 53 of 55 dwarf galaxies are devoid of gas to
limits of M$_{\rm HI}<10^4$ M$_\odot$. Within the virial radius of M31 (266
kpc), 27 of 30 dwarf galaxies are devoid of gas (with limits typically $<10^5$
M$_\odot$). Beyond the virial radii of the Milky Way and M31, the majority of
the dwarf galaxies have detected HI gas and have HI masses higher than the
limits. When the relationship between gas content and distance is investigated
using a Local Group virial radius, more of the non-detected dwarf galaxies are
within this radius (85$\pm1$ of the 93 non-detected dwarf galaxies) than within
the virial radii of the Milky Way and M31. Using the Gaia proper motion
measurements available for 38 dwarf galaxies, the minimum gas density required
to completely strip them of gas is calculated. Halo densities between $10^{-5}$
and $5 \times 10^{-4}$ cm$^{-3}$ are typically required for instantaneous
stripping at perigalacticon. When compared to halo density with radius
expectations from simulations and observations, 80% of the dwarf galaxies with
proper motions are consistent with being stripped by ram pressure at Milky Way
pericenter. The results suggest a diffuse gaseous galactic halo medium is
important in quenching dwarf galaxies, and that a Local Group medium also
potentially plays a role.
