The Kinematics of Emission-Line Galaxies in Clusters from ENACS

Abstract

By using the ENACS data, we have studied the properties of emission-line galaxies (ELG) in clusters. The fraction of ELG in clusters is 16~%; this fraction is slightly dependent on the cluster velocity dispersion, being larger for ``colder'' systems. ELG tend to occur more frequently than other cluster galaxies in substructures. However, only a minor cluster fraction has an ELG population with a mean velocity significantly different from that of the overall cluster population. The velocity distribution of cluster ELG is broader than that of the other cluster galaxies, which translates in a larger observed velocity dispersion. The velocity distribution for ELG in the inner cluster regions suggests that ELG are on mostly radial orbits.

PostScript, 6 pages with figures, to appear in the proceedings of the workshop "Observational Cosmology: from Galaxies to Galaxy Systems", Sesto-Italy, 4-7 July 1995, in a devoted issue of Astrophysical Letters and Communications