| Description |
Recent studies show that compact groups appear to follow an
evolutionary sequence, linked to gas depletion, caused by interactions
in the dense environment. Spitzer photometry of Hickson Compact
Groups show a distinctive gap in IRAC colour-colour space, suggesting
rapid evolution from dusty to dust-free systems which seems to
correlate with HI-depletion in the galaxies, but the mechanism
responsible is poorly understood.
Originally ram-pressure stripping, by analogy with clusters, was thought
to be responsible, but the HI depletion is uncorrelated with the
presence of hot X-ray gas. Based on our recent Spitzer spectroscopy of
a sample of HCGs, we propose a new hypothesis that connects the colour
evolution to the HI-depletion seen in the group galaxies. In this scenario,
galaxies collide with previously stripped tidal debris, that either heats
the disk ISM or strips it, thus shutting off star formation and accelerating
the transition from dusty, gas-rich disks to gas-poor, dust-free systems.
PACS deep [OI]63 and CII[158] maps allow us to look for smooth bow
shock or clumpy shock signatures to discern between heating and
stripping of the disk gas. SPIRE cold dust imaging will allow us to search
for additional evidence of disk disruption and truncation. This project
requires 80.6 hours of observing time. |
