Finding gas-rich dwarf galaxies betrayed by their ultraviolet emission
  We present ultraviolet (UV) follow-up of a sample of potential dwarf galaxy
candidates selected for their neutral hydrogen (HI) properties, taking
advantage of the low UV background seen by the GALEX satellite and its large
and publicly available imaging footprint. The HI clouds, which are drawn from
published GALFA-HI and ALFALFA HI survey compact cloud catalogs, are selected
to be galaxy candidates based on their spatial compactness and non-association
with known high-velocity cloud complexes or Galactic HI emission. Based on a
comparison of their UV characteristics to those of known dwarf galaxies, half
(48%) of the compact HI clouds have at least one potential stellar counterpart
with UV properties similar to those of nearby dwarf galaxies. If galaxies, the
star formation rates, HI masses, and star formation efficiencies of these
systems follow the trends seen for much larger galaxies. The presence of UV
emission is an efficient method to identify the best targets for spectroscopic
follow-up, which is necessary to prove that the stars are associated with the
compact HI. Further, searches of this nature help to refine the salient HI
properties of likely dwarfs (even beyond the Local Group). In particular, HI
compact clouds considered to be velocity outliers relative to their neighbor HI
clouds have the most significant detection rate of single, appropriate UV
counterparts. Correcting for the sky coverage of the two all-Arecibo sky
surveys yielding the compact HI clouds, these results may imply the presence of
potentially hundreds of new tiny galaxies across the entire sky.
