Galaxy Alignments as a Probe of the Dynamical State of Clusters

We present indications, based on a sample of 303 Abell clusters, for arelation between the dynamical state of clusters and the alignments of galaxymembers with their parent cluster major axis orientation as well as with thelarge scale environment within which the clusters are embedded. The statisticalresults are complemented with a deep, wide-field case study of galaxyalignments in the cluster A521, which is characterised by multiple mergingevents (Maurogrdato et al 2000, Ferrari et al. 2003) and whose galaxy membersshow a strong alignment signal out to $\sim 5 h^{-1}$ Mpc. Our results showthat galaxy alignments appear to be stronger the more dynamically young is thecluster, especially when found in high-density environments. This relationcomplements the recently found {``Cluster Substructure - AlignmentConnection''} (Plionis & Basilakos 2002) by which dynamically young clusters,found in high-density environments, show stronger cluster-cluster alignments.Comment: 28 pages, 10 figures, accepted for publication in Ap