092030

The galaxy cluster PLCK G165.7+67.0 (z=0.35) is in the top 1 % brightest sourcesin the Planck sky as a result of strong lensing of background star-forminggalaxies at z=2. The mass estimated from the lens model appears inconsistentwith the lack of X-ray detection in the ROSAT/RASS survey but may be explainedby a non-equilibrium state of the cluster as indicated by its bimodal galaxydistribution and extended radio halo as well as the presence of two NarrowAngle Tail (NAT) galaxies. We request a 75ks XMM observation to determine thecluster???s dynamic state which enables us to measure the position of the X-rayhalo(s) and to search for shocks. These complementary capabilities will greatlyaid the interpretation of the upcoming JWST observations of this cluster. [truncated! Please see actual data for full text]