Molecular Gas and Infrared Emission in HCG 31 AND HCG 92 (Stephan\u27s Quintet) and Tidal Interactions in Compact Group Environment

We present the interferometric measurements of 2.6 mm CO (J 5 13 0) emission (uFWHM 1 50) and the analysis of IRAS HIRES images of two Hickson compact groups HCG 31 and HCG 92 (“Stephan’s Quintet”). The far-infrared (FIR) emission is concentrated to a single region in HCG 31 while it is clearly extended and peaks near the group center in HCG 92. CO emission is weak in HCG 31, and the brightest peak occurs in the overlap region between the galaxies A and C. CO emission is detected only in galaxy C (NGC 7319) in HCG 92, and the distribution is highly asymmetric. No CO emission is detected in the interacting pair HCG 92 B and D (NGC 7318 A and B). Gas stripping and star formation by continuous tidal disruptions in compact group environment are discussed as possible explanations for the observed CO deficiency and peculiar molecular gas distribution in HCG 31 and HCG 92