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Unformatted text preview: it's illegible on the scan, the left column contains A1367, SC 0627-54, and A2256, while on the right we see A262, 2199 (a prominent cD cluster), and 85. There's a large collection of optical/X-ray comparisons available among Ray White's cluster mug shots This XMM-Newton view of the Coma cluster shows the internal structure of even such a rich and relaxed assemblage (ESA image): The X-ray spectra reveal lines of highly ionized Fe, indicating that the gas has been processed - it came from galaxies early on, rather than being primordial. The galaxy motions in the cluster are an ample (but perhaps not the only) heating source, since kT ~ m p v 2 . A typical velocity dispersion 700 km/s implies T ~ 6 x 10 7 K from this source alone. Extra heating sources may be sought from the correlation between velocity dispersion and ICM temperature, or considering the specific entropy of the gas....
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