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arXiv · 1203.1700

Suzaku observations of the Hydra A cluster out to the virial radius

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
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Abstract

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 in a filament direction and a void direction of the large-scale structure of the Universe, respectively. The X-ray emission and distribution of galaxies elongate in the filament direction. The temperature profiles in the two directions are mostly consistent with each other within the error bars and drop to 1.5 keV at 1.5 r_500. As observed by Suzaku in hot clusters, the entropy profile becomes flatter beyond r_500, in disagreement with the r^1.1 relationship that is expected from accretion shock heating models. When scaled with the average intracluster medium (ICM) temperature, the entropy profiles of clusters observed with Suzaku are universal and do not depend on system mass. The hydrostatic mass values in the void and filament directions are in good agreement, and the Navarro, Frenk, and White universal mass profile represents the hydrostatic mass distribution up to ~ 2 r_500. Beyond r_500, the ratio of gas mass to hydrostatic mass exceeds the result of the Wilkinson microwave anisotropy probe, and at r_100, these ratios in the filament and void directions reach 0.4 and 0.3, respectively. We discuss possible deviations from hydrostatic equilibrium at cluster outskirts. We derived radial profiles of the gasmass- to-light ratio and iron-mass-to-light ratio out to the virial radius. Within r_500, the iron-mass-to-light ratio of the Hydra A cluster was compared with those in other clusters observed with Suzaku.

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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. 2012-06-25. Suzaku observations of the Hydra A cluster out to the virial radius. https://doi.org/10.1093/pasj%2F64.5.95

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