Environmental processing of galaxies in HI-rich groups
  We present and explore the resolved atomic hydrogen (HI) content of 13
HI-rich and late-type dominated groups denoted `Choirs'. We quantify the HI
content of the Choir galaxies with respect to the median of the HI-mass
fraction ($f_{\textrm{HI}}$) of their grandparent HIPASS sample. We find that
the HI mass fraction of the Choir galaxies is dispersed around the HIPASS
median in the range $-1.4 \leq \Delta f_{\textrm{HI}}\textrm{[dex]}\leq 0.7$,
from HI-excess to HI-deficient galaxy regime. The HI-excess/HI-deficient
galaxies contain more/less than 2.5 times their expected HI content with
respect to the HIPASS median. We show and discuss that the environmental
processing in Choirs occurs via tidal stripping and galaxy mergers. Our
analysis suggests that tidal stripping contributes to the loss of the HI, while
galaxy mergers contribute to the enhancement of the HI. Exploring the
mid-infrared properties of Choir galaxies we find possible environmental
processing in only nine Choir galaxies, which indicates that environmental
processing is more perceptible in the HI content than the mid-infrared
properties. Moreover, we find that environmental processing occurs in Choir
groups regardless of their global environment, whether they are in isolation or
in proximity to the denser structures, such as cosmic web filaments. We explore
possible scenarios of the Choirs evolution, taking into account their HI
content, velocity dispersion, crossing time and their global environment. We
conclude that the most likely evolution for the majority of Choir groups is
that they will become more compact as their members undergo multiple HI-rich
mergers.
