  High-velocity clouds (HVCs) are clouds of HI seen around the Milky Way with
velocities inconsistent with Galactic rotation, have unknown distances and
masses and controversial origins. One possibility is that HVCs are associated
with the small dark matter halos seen in models of galaxy formation and
distributed at distances of 150 kpc - 1 Mpc. We report on our attempts to
detect the analogs to such putative extragalactic clouds in three groups of
galaxies similar to our own Local Group using the ATNF Parkes telescope and
Compact Array. Eleven dwarf galaxies were found, but no HI clouds lacking stars
were detected. Using the population of compact HVCs around the Milky Way as a
template, we find that our non-detection of analogs implies that they must be
clustered within 160 kpc of the Milky Way (and other galaxies) with an average
HI mass <4x10^5 M(sun) at the 95% confidence level. This is in accordance with
recent limits derived by other authors. If our groups are true analogs to the
Local Group, then this makes the original Blitz et al. and Braun & Burton
picture of HVCs residing out to 1 Mpc from the Milky Way extremely unlikely.
The total HI mass in HVCs, < 10^8 M(sun), implies that there is not a large
reservoir of neutral hydrogen waiting to be accreted onto the Milky Way. Any
substantial reservoir of baryonic matter must be mostly ionized or condensed
enough as to be undetectable.
