The Neutral Hydrogen Properties of Galaxies in Gas-rich Groups
  We present an analysis of the integrated neutral hydrogen (HI) properties for
27 galaxies within nine low mass, gas-rich, late-type dominated groups which we
denote "Choirs". We find that majority of the central Choir galaxies have
average HI content: they have a normal gas-mass fraction with respect to
isolated galaxies of the same stellar mass. In contrast, we find more satellite
galaxies with a lower gas-mass fraction than isolated galaxies of the same
stellar mass. A likely reason for the lower gas content in these galaxies is
tidal stripping. Both the specific star formation rate and the star formation
efficiency of the central group galaxies are similar to galaxies in isolation.
The Choir satellite galaxies have similar specific star formation rate as
galaxies in isolation, therefore satellites that exhibit a higher star
formation efficiency simply owe it to their lower gas-mass fractions. We find
that the most HI massive galaxies have the largest HI discs and fall neatly
onto the HI size-mass relation, while outliers are galaxies that are
experiencing interactions. We find that high specific angular momentum could be
a reason for galaxies to retain the large fraction of HI gas in their discs.
This shows that for the Choir groups with no evidence of interactions, as well
as those with traces of minor mergers, the internal galaxy properties dominate
over the effects of residing in a group. The probed galaxy properties
strengthen evidence that the Choir groups represent the early stages of group
assembly.
