Velocity Gradients in the Intracluster Gas of the Perseus Cluster

Abstract

We report the results of spatially resolved X-ray spectroscopy of 8 different ASCA pointings distributed symmetrically around the center of the Perseus cluster. The outer region of the intracluster gas is roughly isothermal, with temperature ~ 6-7 keV, and metal abundance ~ 0.3 Solar. Spectral analysis of the central pointing is consistent with the presence of a cooling flow and a central metal abundance gradient. A significant velocity gradient is found along an axis at a position angle of \~135 deg, which is ~ 45 deg discrepant with the major axis of the X-ray elongation. The radial velocity difference is found to be greater than 1000 km/s/Mpc at the 90% confidence level. Simultaneous fittings of GIS 2 & 3 indicate that the velocity gradient is significant at the 95% confidence level and the F-test rules out constant velocities at the 99% level. Intrinsic short and long term variations of gain are unlikely (P < 0.03) to explain the velocity discrepancies.