XMM observes ClJ0152.7-1357: A massive galaxy cluster forming at merger crossroads at z=0.83

We present an analysis of a 50ks XMM 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 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^{+0.3}_{-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.