GINGA and EXOSAT observations of the Perseus cluster of galaxies

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Abstract
We report observations of the Perseus cluster of galaxies made using the Ginga and EXOSAT satellites. Our results from Ginga indicate that the region around the centrally dominant galaxy NGC 1275 is well described by a model incorporating emission from an isothermal, diffuse plasma of temperature ≈ 6.3 keV, metal abundance ≈ 0.4 solar, a cooling flow with a mass deposition rate |$\approx\,270\,{M}_{\odot}\,\text{yr}^{-1}$| and photoelectric absorption from a galactic column density of |$1.3\,\times\,{10}^{21}\,\text{atom}\,\text{cm}^{-2}$|⁠. This value is also consistent with the EXOSAT observations. The metal abundance is constrained to within 5 per cent making this the most precise determination of the metallicity of a cluster to date. We find no evidence for a significant power-law component from the active nucleus of NGC 1275 in either data set. A systematic series of paintings at different regions of the cluster made with Ginga reveal no evidence for a radial dependence of metal abundance but do indicate the possibility of some large-scale temperature variation. Finally, a simple test has been performed to determine whether the intracluster gas is locally isothermal. Although we find that the gas is best modelled by an isothermal distribution, our data do allow a moderate (⁠|$\Delta kT\,\approx\,3.5\,\text{keV}$|⁠) temperature spread, sufficient to account for the widespread mass deposition known to occur within the central cooling flow.

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