The Core of the Virgo Cluster

Abstract

We are now extending the CfA Redshift Survey (e.g. see Huchra et al. 1983) to cover a large area of the sky and to reach fainter limits. One of the logical first steps was a more detailed study of the core of the Virgo cluster. Although it is not terribly rich, the Virgo cluster is several times nearer than any other rich cluster in the northern celestial hemisphere. Thus it is well suited for studies of the faint end of the cluster luminosity function. In addition, its internal dynamics are of great interest in x-ray studies, and for the determination of the mean mass density of the cluster and the mean mass-to-light ratio for cluster galaxies. The Virgo cluster also plays an important role in the determination of the Hubble constant, due to its distortion of the local Hubble flow and the use of cluster members as calibrators of the tertiary distance indicators. Because of its unique position as the core of our own Supercluster, the Virgo cluster has been the subject of many previous studies (e.g. Sulentic 1977, Sandage and Tammann 1976, de Vaucouleurs and de Vaucouleurs 1973, Kraan-Korteweg 1982, and Eastmond 1977). Most of these used substantially fewer velocities than the present study.