Cooling Flows in Clusters and Galaxies by Craig L. Sarazin (auth.), A. C. Fabian (eds.)

By Craig L. Sarazin (auth.), A. C. Fabian (eds.)

X-ray astronomers found the diffuse gasoline in clusters of galaxies approximately twenty years in the past. It was once later discovered that the relevant fuel density in a few clusters, and in elliptical galaxies, is so excessive that radiative cooling is an important strength loss. The cooling time of the gasoline decreases speedily in the direction of the centre of the cluster or galaxy and is under a Hubble time in the innermost few hundred kiloparsecs. This leads to a cooling move within which the fuel density rises with a purpose to continue strain to help the load of the overlying fuel. the speed at which mass is deposited by means of the move is inferred to be a number of 1000's of sun lots according to 12 months in a few clusters. The fraction of clusters within which cooling flows are stumbled on may possibly exceed 50 consistent with cent. Small flows most likely happen in most traditional elliptical galaxies that aren't in wealthy clusters. the results of this easy phenomenon are profound, for we seem to be witnessing the continued formation of the imperative galaxy. specifically, due to the fact that lots of the gasoline is undetected as soon as it cools less than approximately three million ok, it seems that to shape darkish subject. there's no this is because it's going to be detectable with present recommendations if each one cooling proton in simple terms recombines as soon as and the problem condenses into items of low mass.

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0:: 0 Z ~ -3J -3 I' ~ 10' A2199 A 262 kpc kpc (/) I

1. Method We have derived quantitative parameters of cluster emission by modelling the x-ray surface brightness distribution as observed with the Einstein IPC. This requires that the distribution be (approximately) spherically symmetric. We omit serendipitous (foreground/background) sources, subtract an appropriate (energy, detector pulse height, and position dependent) background, and properly model the point response function of the detector (pulse height and energy dependent). For details of the analysis see Jones and Forman (1984).

0 * ** 00 00 00 0.. 0 00 2" ..... i9 C. I- • ,.... 1 o 0 cooling o o It) 0 o 5 10 50 100 Figure 7. Central densities and temperatures for the total sample. Circles indicate cooling flows. 5. COOLING FLOW RESULTS Figure 7 shows the central density and temperature for all clusters in the sample (from the IPC observations only). The stars and circles divide thf' clusters into those with central cooling times longer and shorter than th = 2 X 1010 yr respectively. There are 43 cooling flows.

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