THE HOTTEST comma RELAXED HIGH-Z GALAXY CLUSTER

We propose an 84ks observation of the massive galaxy cluster ClJ1226.9+3332 atz0.89 to detect its emission out to the virial radius (Rv). This cluster is thehottest known at z>0.6 (kT11.5keV), is highly luminous, and uniquely, appearsrelaxed. The proposed observation uses the sensitivity of XMM to trace theemission out to Rv, construct a detailed temperature profile, and map surfacebrightness and temperature variations on small and large scales. Combined withour existing highquality multiwavelength data, this will allow us to measurethe cluster.s properties (eg total mass, gasmass fraction) with anunprecedented degree of accuracy. These measurements will enable newcosmological constraints to be placed, and provide the benchmark for comparisons with other highz clusters. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]