Groups of galaxies. III - The CfA survey

A statistically homogeneous group catalog (CfA) is based on the CfA redshift survey (Huchra et al.) is presented. Groups in the catalog are all density enhancements in redshift space of a factor greater than 20. Group members are identified according to the procedure described in a previous study (Huchra and Geller) of a shallower whole-sky sample. All groups contain at least three members. Of the 176 groups in the CfA catalog, 102 have been identified in one or more previous studies. Because the utilized algorithm searches for volume rather than surface density enhancements, the groups in a given region generally change only through the addition of fainter members when the magnitude limit of the galaxy catalog increases. In the region of overlap, agreement between the shallow catalog and the CfA catalog is excellent.