Star Formation in Las Campanas Compact Groups

Compact groups (CGs) of galaxies offer an exceptional laboratory for the study of dense galaxian environments — where interactions, tidally induced activity, and mergers are expected to be at their highest rate of occurrence. Here, we present first results from a new catalogue of compact groups, one based upon the Las Campanas Redshift Survey (LCRS). Using the equivalent width of [O II] λ 3727, we have studied the star formation activity in LCRS CGs: we find strong evidence of depressed star formation in CGs relative to that in loose groups or the field. Although much of this effect can be ascribed to morphological mix (CGs contain a high fraction of early-type galaxies), there is some evidence that the star formation rate in late-type galaxies is particularly deficient — perhaps only one-half to one-third that of field spirals. We conclude that gas stripping mechanisms may play a role in CG environments. Subject headings: catalogs – galaxies: clusters: general – galaxies: interactions – galaxies: starburst Visiting Scientist, Fermi National Accelerator Laboratory Hubble Fellow Also: Dept. of Astronomy, Yale University, New Haven, CT 06520-8101; [email protected]