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

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 e ect 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 proÐle, the strong central excess above a single b model, identiÐed in the Einstein and ROSAT data, is also found in the harder energy band ([4 keV). A simultaneous Ðt of Ðve annular spectra taken with the GIS instru-ment shows a radial distribution of the temperature and metal abundance. A signiÐcant central enhance-ment in the abundance distribution is found, while the temperature proÐle suggests that the ICM is approximately isothermal, with a temperature of D3.5 keV. The ROSAT position-sensitive proportional counter (PSPC) spectrum in the central region indicates a signiÐcantly lower temperature than the 1@ .5 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 Ñow model. In both cases, the hot-phase gas with a temperature of D3.5 keV occupies more than 90% of the total emission measure within from the 1@ .5 cluster center. The estimated mass of the cooler (0.5È0.7 keV) component is D(2È6) ] 109 which is M _ , comparable to the mass of hot halos seen in non-cD ellipticals. The cooling Ñow model gives the mass deposition rate of 60 ^ 30 yr~1, an order of magnitude lower than the previous estimation. M _ Subject headings : galaxies : clusters : individual (Hydra A) È intergalactic medium È X-rays : galaxies