What is the origin of a diffuse IGM in compact groups?

Since the discovery of large HI deficiencies in Hickson Compact Groups (HCGs), the fate of atomic gas in these systems has been a mystery. We previously proposed an evolutionary scenario where the amount of HI decreases with the secular evolutionary state of a group. But what physical processes give rise to this decrease? Our X-ray study of 8 of the most HI deficient HCGs suggested that galaxy-IGM interaction is not the dominant mechanism driving cold gas out of group members (Rasmussen et al 2008). In order to explore this issue further, we have gathered VLA and GBT data for a complete distance-limited sample of 22 HCGs with normal, deficient, and highly deficient HI properties. The GBT observations (Borthakur et al 2010) revealed evidence for a significant HI excess compared with the interferometer measurements, and this excess appears to increase with the evolutionary phase of the group, possibly associated with the diffusing tidal debris in the IGM. Here, we present the first detailed comparison of VLA & GBT data in Stephan's Quintet (HCG 92) as a first step to examine the spatial and kinematic link between the high surface brightness to diffuse HI emission in these groups. Our preliminary results suggest that tidal tails could evolve to a diffuse neutral component, as suggested in Verdes-Montenegro et al (2001) and Borthakur et al (2010).