Spatial Distributions of A3558 in the Core Region of the Shapley
Supercluster
F. Akimoto1, K. Kondou1, A. Furuzawa1, Y. Tawara1, K. Yamashita1
1: Department of Physics, Nagoya University
Abstract
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 ~300 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' x 4' scale, the two poor clusters show nearly isotropic
temperature distributions, while the three Abell clusters are
asymmetric. A3558 was analyzed with a 2' x 2' 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 ~320 kpc
was also found to the southeast, ~12' 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.