Is There an Enormous Cold Front at the Virial Radius of the Perseus Cluster?

We present new XMM-Newton observations extending the mosaic of Perseus cluster out to virial radius west. Previous studies with ROSAT have reported a large excess in surface brightness west, possibly result scale gas sloshing, but lacked spatial resolution and depth determine if this lay behind cold front. In our XMM we found that there is sharp edge X-ray near (1.7Mpc) width comparable mean free path. The temperature measurements obtained Suzaku data across show increases sharply outside edge. All these properties are consistent being largest front ever observed galaxy cluster. also find second 1.2Mpc from core, which appears be Our results indicate magnetic fields able stabilize fronts against turbulence all way radius. By comparing numerical simulations, require impact parameter, low mass ratio mergers can produce fast motions without destroying core.