An investigation of cooling flows and general cluster properties from an X-ray image deprojection analysis of 207 clusters of galaxies

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Abstract
In this paper we present an X-ray image deprojection analysis of Einstein Observatory imaging data on 207 clusters of galaxies. The resulting radial profiles for luminosity, temperature and electron density variations are determined from the cluster surface-brightness profiles according to gravitational potential constraints from average X-ray temperatures and optical velocity dispersions. This enables us to determine cooling flow and other cluster properties, such as baryon fractions, Sunyaev-Zel'dovich microwave decrements and Thomson depths. From the results we have compiled a catalogue of the detected cooling flows, and investigated their effects on general cluster properties. To assist in the analysis, we have constructed self-consistent correlations between the cluster X-ray luminosity, temperature and optical velocity dispersion, using ‘orthogonal distance’ regression to account for errors in both dimensions of the data. These fits indicate that, in general, the temperatures of clusters are isothermal, and that they have spectral β-values consistent with unity (if the dependence of luminosity on temperature is assumed to be quadratic). We find that the X-ray luminosity, temperature and optical velocity dispersion relations depend significantly on the cooling flow mass-deposition rate, through characteristic differences in the density profiles. Clusters of similar cooling flow mass-deposition rate exhibit self-similar density profiles, with larger cooling flows showing higher central densities. This leads to scatter in the luminosity-related correlations within the X-ray luminosity, temperature and optical velocity dispersion plane. The segregation in density also leads to dispersion in other related properties such as ‘half-light radii’ and baryon fractions. The baryon fraction in the cores of cooling flow clusters appears to be higher, but as the density profiles tend to a similar value at larger radii, irrespective of cooling flow property, so too do the baryon fraction profiles appear to rise to a concordant value of greater than 10 per cent at 1 Mpc. Thus this sample indicates that clusters, as a whole, are inconsistent with primordial nucleosynthesis baryon fraction prediction, for a flat universe, of 6 per cent.
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