Evidence of ram pressure stripping of WLM, a dwarf galaxy far away from
  any large host galaxy
  Dwarf galaxies are affected by all the evolutionary processes normally at
work in galaxies of any mass. As fainter and less massive galaxies, however,
dwarf galaxies are particularly susceptible to environmental mechanisms that
can more easily perturb these systems. Importantly, the presence of nearby
large galaxies are expected to have a profound effect on dwarf galaxies.
Gravitational (especially tidally-induced) effects from the large galaxy can
cause mass to be lost from the dwarf, and the passage of the dwarf through the
gaseous medium surrounding the large galaxy can additionally cause the dwarf to
lose its own gas through a process called ram pressure stripping. Such effects
are considered to be the main sources of difference between "satellite" and
"field" dwarf galaxy populations. Here, we report on new observations of the
gaseous content of Wolf-Lundmark-Melotte (WLM), an archetype of isolated,
gas-rich field dwarf galaxies in the Local Universe, which shows a much more
complex situation. Previous studies of its gaseous disk suggest it has
perturbed kinematics; here, we identify four trailing, extended gas clouds in
the opposite direction to WLM's spatial motion, as well as a spatial offset
between the WLM gas and stars. Overall, the morphology and kinematics of this
gas shows that WLM is undergoing ram pressure stripping, despite being 930 and
830 kpc from the Milky Way and M31, respectively. This finding indicates the
presence of an inter-galactic, gaseous reservoir far from large galaxies whose
evolutionary role on galaxies, both large and small, may not be fully
appreciated.
