Galaxy interactions in loose galaxy groups: KAT-7 and VLA HI
  Observations of the IC 1459 group
  We report on the results from deep HI observations, performed with the Karoo
Array Telescope and with the Karl G. Jansky Very Large Array of the loose
galaxy group centred on the early-type galaxy IC 1459. The main result from our
observations is the detection of a nearly continuous, 500-kpc long HI tail
which crosses the entire group. Earlier observations with the Australia
Telescope Compact Array had shown the presence of a large HI tail in this
galaxy group, but because of the much larger coverage of the new data, the full
extent of this tail is now visible. The HI mass of this structure is 3.1 +- 0.3
10^9 Msun . Based on its morphology and kinematics, we conclude that the tail
consists of gas stripped from NGC 7418 through tidal interactions, with
ram-pressure affects playing at most a minor role. Optical images of the IC
1459 group do not show many indications that galaxy interactions are common in
this group. The HI data reveal a very different picture and show that almost
all gas-rich galaxies in the IC 1459 group have a distorted HI distribution
indicating that many interactions are occurring in this group. This high number
of interactions shows that the processes that drive galaxy transformation are
also occurring in fairly loose galaxy groups.
