ALMA/ACA CO Survey of the IC 1459 and NGC 4636 Groups: Environmental
  Effects on the Molecular Gas of Group Galaxies
  We present new results of a 12CO(J=1-0) imaging survey using the Atacama
Compact Array (ACA) for 31 HI detected galaxies in the IC 1459 and NGC 4636
groups. This is the first CO imaging survey for loose galaxy groups. We
obtained well-resolved CO data (~0.7-1.5 kpc) for a total of 16 galaxies in two
environments. By comparing our ACA CO data with the HI and UV data, we probe
the impacts of the group environment on the cold gas components (CO and HI gas)
and star formation activity. We find that CO and/or HI morphologies are
disturbed in our group members, some of which show highly asymmetric CO
distributions (e.g., IC 5264, NGC 7421, and NGC 7418). In comparison with
isolated galaxies in the xCOLD GASS sample, our group galaxies tend to have low
star formation rates and low H2 gas fractions. Our findings suggest that the
group environment can change the distribution of cold gas components, including
the molecular gas, and star formation properties of galaxies. This is
supporting evidence that pre-processing in the group-like environment can play
an important role in galaxy evolution.
