An optical analysis of the merging cluster Abell 3888

Abstract

In this paper we present new AAOmega spectroscopy of 254 galaxies within a 30 arcmin radius around Abell 3888. We combine these data with the existing redshifts measured in a one degree radius around the cluster and performed a substructure analysis. We confirm 71 member galaxies within the core of A3888 and determine a new average redshift and velocity dispersion for the cluster of 0.1535 ± 0.0009 and 1181 ± 197 km s-1, respectively. The cluster is elongated along an East-West axis and we find the core is bimodal along this axis with two subgroups of 26 and 41 members detected. Our results suggest that A3888 is a merging system putting to rest the previous conjecture about the morphological status of the cluster derived from X-ray observations. In addition to the results on A3888 we also present six newly detected galaxy overdensities in the field, three of which we classify as new galaxy clusters.