An XMM-Newton Measurement of the Fastest Known Cluster Merger in the Universe

To employ galaxy clusters as cosmological standards and astrophysicallaboratories, we must better understand how the cluster dynamical state maps toits observational properties in extreme circumstances, yet fewer than a dozenmergers have velocity measurements reliable enough for detailed modeling. Onedramatic merger, selected for followup Xray observations by its ultrasteepspectrum radio emission, is Abell 2443. Recently, a 98 ksec Chandra observationprovided 2.9sigma evidence that the bulletlike core of A2443 is significantlyblueshifted with respect to its surroundings. We propose deep XMM observationsto answer the question, What is the true line of sight component of the gas.svelocity?.. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]