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X-ray Observations at the Virial Radius of Galaxy Clusters

Matthew George, IoA

We have measured X-ray emission from the outskirts of the cluster of galaxies PKS 0745-191 with Suzaku, determining radial profiles of density, temperature, entropy, gas fraction, and mass. These measurements extend beyond the virial radius to ~1.5 r_200, providing new information about cluster assembly and the diffuse intracluster medium. The temperature is found to decrease by roughly 60% from 0.3-1 r_200. We also see a flattening of the entropy profile near the virial radius and consider the implications this has for the assumption of hydrostatic equilibrium when deriving mass estimates. Putting these observations in the context of simulations and analytical models, we will be able to better understand the role of non-gravitational physics in the outskirts of clusters.