Structure of the X‐Ray–emitting Gas in the Hydra A Cluster of Galaxies

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Abstract
The temperature and abundance structure in the intracluster medium (ICM) of the Hydra A Cluster of galaxies is studied with ASCA and ROSAT. The effect of the large extended outskirts in the point-spread function of the X-ray telescope on ASCA is included in this analysis. In the X-ray brightness profile, the strong central excess above a single β model, identified in the Einstein and ROSAT data, is also found in the harder energy band (>4 keV). A simultaneous fit of five annular spectra taken with the GIS instrument shows a radial distribution of the temperature and metal abundance. A significant central enhancement in the abundance distribution is found, while the temperature profile suggests that the ICM is approximately isothermal, with a temperature of ~3.5 keV. The ROSAT position-sensitive proportional counter (PSPC) spectrum in the central 15 region indicates a significantly lower temperature than the GIS result. A joint analysis of the GIS and PSPC data reveals that the spectra can be described by a two-temperature model as well as by a cooling flow model. In both cases, the hot-phase gas with a temperature of ~3.5 keV occupies more than 90% of the total emission measure within 15 from the cluster center. The estimated mass of the cooler (0.5-0.7 keV) component is ~(2-6) × 109 M☉, which is comparable to the mass of hot halos seen in non-cD ellipticals. The cooling flow model gives the mass deposition rate of 60 ± 30 M☉ yr-1, an order of magnitude lower than the previous estimation.