Spatial Distributions of A3558 in the Core Region of the Shapley Supercluster

The core region of the Shapley supercluster is dominated by three rich Abell clusters and two poor clusters. Since these member clusters are expected to be evolving rapidly in comparison to nonmember clusters because of the high merging rate, it is important to study the member clusters for understanding of the cluster evolution. Since the spatial distributions of gas temperature and metal abundance in each member cluster provide us with information on the interactions and motions of member clusters, they are useful for understanding their dynamics. From the results of eight ASCA pointing observations (total similar to300 ks) of the core region, we obtained parameters of gas temperature, metal abundance, and X-ray luminosity for five member clusters and found that they are similar to the other field clusters not belonging to superclusters observed with ASCA. This result and the mean gravitational mass density of the core region indicate that the members are growing in the same way as the nonmember clusters, and the core of the supercluster is just on the way to contraction. Based on analyses of detailed spatial structures with a 4'x4' scale, the two poor clusters show nearly isotropic temperature distributions, while the three Abell clusters are asymmetric. A3558 was analyzed with a 2'x2' scale, owing to the statistical advantage, and it was revealed that A3558 has clear asymmetric distributions of gas temperature and X-ray surface brightness. This is thought to be caused by cluster-cluster mergings and/or group infallings. A metal-rich region with the size of similar to320 h(50)(-1) kpc was also found to the southeast, similar to12' away from the cluster center of A3558. It is expected that either a remnant of a merged core has been left after a major merging or a group of galaxies has been recently infalling. Thus, the high dynamical activity of A3558 is proved.