XMM-Newton OBSERVES CLJ0152.7−1357: A MASSIVE GALAXY CLUSTER FORMING AT MERGER CROSSROADS AT Z = 0.83

We present an analysis of a 50 ks XMM-Newton observation of the merging galaxy cluster ClJ0152.7−1357 at z = 0.83. In addition to the two main subclusters and an infalling group detected in an earlier Chandra observation of the system, XMM-Newton detects another group of galaxies possibly associated with the cluster. This group may be connected to the northern subcluster by a filament of cool (1.4 −0.1 keV) X-ray emitting gas, and lies outside the estimated virial radius of the northern subcluster. The X-ray morphology agrees well with the projected galaxy distribution in new K-band imaging data presented herein. We use detailed spectral and imaging analysis of the X-ray data to probe the dynamics of the system and find evidence that another subcluster or group has recently passed through the northern subcluster. ClJ0152.7−1357 is an extremely dynamically active system with mergers at different stages occurring along two perpendicular merger axes. Subject headings: cosmology: observations – galaxies: clusters: general – galaxies: high-redshift galaxies: clusters: individual: (ClJ0152.7−1357) – intergalactic medium – X-rays: galaxies