Witnessing the creation of the first shock in a cluster collision

We propose to observe a unique cluster pair 1E2216/1E2215 in earlystage merger.Based on archival shallow Xray data, we discovered a hot gas bridge between thetwo clusters, and a putative shock with Mach number of 1.4 in the middle of thebridge. The bridge region also contains at least three diffuse radio sourceswith very different properties. This is the first time that diffuse radioemission is observed at the site of an early stage merger. We request a totalEPIC exposure of 130 ks to measure the shock heating, and to search for thepredicted vertical shock in this unique system. The combined Xray and radiodata will determine the thermal vs. nonthermal energy partition of the shock. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]