Properties of dense galaxy groups and the implications of their existence

Galaxy counts are reported within 1 deg of the 100 dense groups cataloged by Hickson (1982). The results suggest that a much smaller fraction of the groups can be explained as chance alignments than has recently been suggested by Mamon (1986). Thus, it appears that at least 100 dense physical groups exist on the sky which cannot be short-lived transient systems and often contain one or more discordant redshift members. The possibility that the galaxies in these groups formed together relatively recently and may be related to some of the galaxy 'nests' of Vorontsov-Velyaminov (1962) is considered. It is suggested that the discordant redshift members are somehow related to this recent formation. Tests of these suggestions are proposed.