THE BIRTHPLACE OF COMPACT-GROUPS OF GALAXIES

We use complete redshift surveys to study the redshift neighborhoods of 38 Hickson compact groups (HCGs). Twenty-nine of these HCGs (76%) are embedded in rich looser systems which we call HCG associations. Analysis of the redshift neighborhood of HCGs outside the CfA survey suggests that most HCGs are embedded in more extended physical systems. Rich loose groups extracted from the CfA survey [Ramella et al. in preparation (1994)] have physical properties similar to those of the HCG associations. These rich loose groups often contain compact configurations. N-body experiments [Diaferio et al. AJ, 107, 868 (1994)] suggest that compact configurations analogous to HCGs form continually during the collapse of rich loose groups. These observational and numerical results suggest that rich loose groups are the birthplace of HCGs.