A2440 : Compact Merger just before Collapse

The physics of the compression wave forming at the beginning of major clustermergers is still not fully understood because of the lack of Xray observationsof equal mass merging clusters close enough but before the first maximum corecollapse. We propose to observe with XMMNewton a carefully selected clusterdisplaying the densest bimodal distribution in the optical and Xray. Thesedata and parallel optical observations will allow, in conjunction with twoothers already observed bimodal clusters, for the first time to directlydetermine the physical conditions (such as density, temperature, gas mixing) inthe compressed hot gas and the interplay of the compression waves with the starformation rates of the galaxies. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]