HI debris in the IC 1459 galaxy group

Abstract

We present HI synthesis imaging of the giant elliptical galaxy IC 1459 and its surroundings with the Australia Telescope Compact Array. Our search for extended HI emission revealed a large complex of HI clouds near IC 1459, likely to be the debris from tidal interactions with neighbouring galaxies. The total HI mass (~109M⊙) in the detected clouds spans 250 kpc from the north-east of the gas-rich spiral NGC 7418A to the south-east of IC 1459. The extent and mass of the HI debris, which shows rather irregular morphology and kinematics, are similar to those in other nearby groups. Together with HI clouds recently detected near two other IC 1459 group members, namely IC 5270 and NGC 7418, using phased-array feeds on the Australian Square Kilometre Array Pathfinder, the detected debris make up a significant fraction of the group's intergalactic medium.