Velocity distribution of Virgo Cluster galaxies

Abstract

Several effects of the general population of the Local Supercluster on observed properties of the Virgo Cluster are analyzed. Two subgroups are identified in the field of the Virgo Cluster that are most likely beyond the Virgo distance. Combined with an intrusion of the W cloud into the field of the cluster, this clumped component accounts for about 9 percent of the galaxies in the sample complete to mp = 14.5. Evidence is also presented of a near Hubble expansion of galaxies in the outer 2 deg of the cluster suggesting that the flow within the supercluster may be generally retarded, but not very disturbed otherwise. The numerical models suggest that the large difference between the T less than 0 and T greater than 0 velocity dispersions cannot have arisen from the accidental inclusion of a smoothly distributed supercluster population and is hardly affected by the subtraction of the clumped component identified. Several different approaches suggest a cluster mean velocity in the range of 960-1000 km/s with 980 km/s a 'best' estimate.