Takuya Sato, Toru Sasaki, Kyoko Matsushita, Eri Sakuma, Kosuke Sato, Yutaka Fujita, Nobuhiro Okabe, Yasushi Fukazawa, Kazuya Ichikawa, Madoka Kawaharada, Kazuhiro Nakazawa, Takaya Ohashi, Naomi Ota, Motokazu Takizawa, Takayuki Tamura
We report Suzaku observations of the northern half of the Hydra A cluster out to ~1.4 Mpc, reaching the virial radius. This is the first Suzaku observations of a medium size (kT ~3 keV) cluster out to the virial radius. Two observations were conducted, north-west and north-east offsets, which continue into a filament and a void of the large-scale structure of the Universe, respectively. The X-ray emission and distribution of galaxies elongate towards the filament. The temperature profiles toward the two directions are mostly consistent within error bars and drop to 1.5 keV at 1.5r_500. As observed by Suzaku in hot clusters, the entropy profile becomes flatter beyond r_500 and disagrees with the r^1.1 relation that is expected from accretion shock-heating models. When scaled with average intracluster medium (ICM) temperature, the entropy profiles of clusters observed with Suzaku are universal without dependence on system mass. The hydrostatic mass values toward the void and the filament agree well, and the Navarro, Frenk, and White (NFW) universal mass profile represents the obtained hydrostatic mass distribution up to ~ 2r_500. Beyond r_500, the ratio of gas mass to hydrostatic mass exceeds the WMAP result, and at r_100, these ratios toward the filament and void directions reach 0.4 and 0.3, respectively. We discussed about possible deviations from hydrostatic equilibrium at cluster outskirts. The iron-massto- light ratio (IMLR) profile is larger than within r500 by a factor of 2, which was observed in other clusters with Suzaku, and becomes flatter from r_500 to 2 r_500.
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http://arxiv.org/abs/1203.1700
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