Properties of Very Luminous Galaxies

Recent analysis of the data from the Southern Sky Redshift Survey extension (SSRS2) based on cell counts and the two-point correlation function has shown that very luminous galaxies are much more strongly clustered than fainter galaxies. In fact, the amplitude of the correlation function of very luminous galaxies (L > L*) asymptotically approaches that of R ≥ 0 clusters. In this paper we investigate the properties of the most luminous galaxies, with blue absolute magnitudes MB ≤ -21. We find that (1) the population mix is comparable to that in other ranges of absolute magnitude; (2) only a small fraction are located in bona fide clusters; (3) the bright galaxy–cluster cross-correlation function is significantly higher on large scales than that measured for fainter galaxies; (4) the correlation length of galaxies brighter than MB ∼ -20.0, expressed as a function of the mean interparticle distance, appears to follow the universal dimensionless correlation function found for clusters and radio galaxies; (5) a large fraction of the bright galaxies are in interacting pairs, while others show evidence for tidal distortions and some appear to be surrounded by faint satellite galaxies. We conclude that very luminous optical galaxies differ from the normal population of galaxies in both clustering and other respects. We speculate that this population is a highly biased tracer of mass, being associated with dark halos with masses more comparable to clusters than to typical loose groups.