The COMA/A1367 Supercluster and Its Environs

The three-dimensional galaxy distribution in the region of space surrounding the two rich clusters Coma and A1367 is analyzed by using a nearly complete redshift sample of 238 galaxies with m, < 15.0 in a 260 degree2 region of the sky; 44 of these redshifts are reported here for the first time. We find that the two clusters are enveloped in a common supercluster which also contains four groups and a population of isolated galaxies. The least dense portions of the ComalA1367 supercluster have a density which is approximately 6 times that of the Local Supercluster in the regions of our own Galaxy. In front of the Coma/A1367 supercluster we find eight distinct groups or clouds but no evidence for a significant number of isolated "field" galaxies. In addition, there are large regions of space with radii r > 20 h-l Mpc where there appear to be no galaxies whatever. Since tidal disruption is probably responsible for the isolated component of supercluster galaxies, the observations suggest that all galaxies are (or once were) members of groups or clusters. A number of related topics with more general significance are also discussed. (1) The size-to-separation ratio for foreground groups indicates that the redshift of group formation is z 8 9. (2) There is a general correlation between the volume mass density of a galaxy system and the morphologies of the component galaxies. (3) Finally, we speculate that all clusters of richness class z 2 2 are located in superclusters. Subject headings: galaxies : clusters of galaxies: redshifts