XMM-Newton Study of A3562 and Its Immediate Shapley Environs

Abstract

Using a mosaic of six XMM-Newton observations, we study the hydrodynamic state of A3562, a cluster in the center of the Shapley supercluster. The X-ray image reveals a sharp surface brightness gradient within the core of A3562, a 200 kpc ridge extending to the southwest. A nearby group, SC 1329-313, imaged within this program also exhibits a tail aligned with the ridge. Study of the pressure and entropy identified the ridge with a 40% pressure enhancement. An associated Mach number of 1.15 relative to a polytropic sound speed for a 5 keV plasma requires the velocity of the group to be 1400 km s^-1, while the projected velocity difference between the cluster and the group amounts to 1200-1500 km s^-1. Apparent disruption of the group, if attributed to the ram pressure, also requires the velocity of the group in the cluster frame to amount to 1700+/-150 km s^-1. The sharp surface brightness gradient at the center is identified with a contact discontinuity, which together with dovetails in the large-scale entropy distribution reveals a sloshing of the bright cluster galaxy in response to the passage of the SC 1329-313 group. Using the extent of the low-entropy tails in A3562, we estimate the amplitude of sloshing motion to be 200h^-1₇₀ kpc and the oscillation frequency to be 1 Gyr.