Hot Gas in Clusters of Galaxies

Hot Gas in Clusters - 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

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Hot Gas in Clusters of Galaxies Velocity dispersions suggest that about 90% of the mass in clusters is not in individual galaxies. Amounts of mass comparable to that in the galaxies (but not the dynamical total) are implied by X-ray emission from hot gas and radio "tails" bent by galaxy motion through an intracluster medium. Cluster X-ray sources have been reviewed by Forman and Jones 1982 (ARA&A 20, 547) and Sarazin 1986 (Rev. Mod. Phys. 58, 1). The gas has temperature 4-7 keV corresponding to the temperature associated with the cluster velocity dispersion and spectra consistent with thermal brehmsstrahlung. The gas is not usually associated with individual galaxies, unless a dominant one is at the center of the cluster potential: from Fig 1 of Forman and Jones (taken from the ADS), one can see the range in X-ray morphologies, from the dispersed and irregular morphology of the clusters on the left to the increasingly concentrated forms on the right. Since
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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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This note was uploaded on 11/10/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.

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Hot Gas in Clusters - 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

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