| 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 thepresence 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 OI63 and CII158 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. |
