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 gas-mass-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.

We report the first observations of metal distributions in the intracluster medium of the Centaurus cluster up to $\sim\ $ 0.17 $\ r_{180}$ with Suzaku. Radial profiles of the O, Mg, Si, S, Ar, Ca, and Fe were determined at the outer region of the cluster, and their variations appear to be similar to each other. Within the cool core region ( $r$$<$ 0.045 $\ r_{180}$ ), all of the metal distributions sharply increased toward the center. In the central region ( $r$$<$ 0.015 $\ r_{180}$ ), the abundances of Si, S, Ar, Ca, and Fe were 1.5–1.8 solar, while those of O and Mg were approximately 1 solar. The derived abundance ratios of O and Mg to Fe were slightly lower than those of a set of other clusters. In contrast, the calculated mass-to-light ratios (MLRs) for O, Mg, and Fe were larger than those of the other clusters. For the outer region of the cool core ( $r$$>$ 0.07 $\ r_{180}$ ), all of the abundances were almost constant at 0.5 solar. The derived MLRs were comparable to those of the other clusters. This suggests that the cD galaxy of the Centaurus cluster efficiently supplies more Fe than the other clusters.

We analyzed XMM-Newton data of the Perseus cluster out to ∼1 Mpc, or approximately half the virial radius. Using the flux ratios of Lyα lines of H-like Si and S to Kα line of He-like Fe, the abundance ratios of Si/Fe and S/Fe of the intracluster medium (ICM) were derived using the APEC plasma code v2.0.1. The temperature dependence of the line ratio limits the systematic uncertainty in the derived abundance ratio. The Si/Fe and S/Fe in the ICM of the Perseus cluster show no radial gradient. The emission-weighted averages of the Si/Fe and S/Fe ratios outside the cool core are 0.91 ± 0.08 and 0.93 ± 0.10, respectively, in solar units according to the solar abundance table of Lodders (2003). These ratios indicate that most Fe was synthesized by supernovae Ia. We collected K-band luminosities of galaxies and calculated the ratio of Fe and Si mass in the ICM to K-band luminosity, iron-mass-to-light ratio (IMLR) and silicon-mass-to-light ratio (SMLR). Within ∼1 Mpc, the cumulative IMLR and SMLR increase with radius. Using Suzaku data for the northwest and east directions, we also calculated the IMLR out to ∼ 1.8 Mpc, or about the virial radius. We constrained the SMLR out to this radius and discussed the slope of the initial mass function of stars in the cluster. Using the cumulative IMLR profile, we discuss the past supernova Ia rate.

We studied the distributions of Si, Fe, and Ni in the intracluster medium (ICM) of the Coma cluster, one of the largest clusters in the nearby universe, using XMM-Newton data up to 0.5 r 180 and Suzaku data of the central region up to 0.16 r 180 . Using the flux ratios of Lyα line of H-like Si and 7.8 keV line blend to Kα line of He-like Fe, the abundance ratios of Si to Fe and Ni to Fe of the ICM were derived using APEC model v2.0.1. The Si/Fe ratio in the ICM of the Coma cluster shows no radial gradient. The emission weighted averages of the Si/Fe ratio in the ICM within 0.0-0.2 r 180 , 0.2-0.5 r 180 , and 0.0-0.5 r 180 are 0.97 ± 0.11, 1.05 ± 0.36 and 0.99 ± 0.13, respectively, in solar units using the solar abundance table by Lodders (2003). These values are close to those of smaller clusters and groups of galaxies. Using the Suzaku data of the central region, the derived Ni/Fe ratio of the ICM is 0.6-1.5 in solar units, according to the same solar abundance table. The systematic difference in the derived abundance ratios by different plasma codes are about 10%. Therefore, for the ICM in the Coma cluster, the abundance pattern of Si, Fe, and Ni is consistent with the same mixture of the yields of supernova (SN) II and SN Ia in our Galaxy. Within 0.5 r 180 , the cumulative iron-mass-to-light ratio increases with radius, and its radial profile is similar to those of relaxed smaller clusters with cD galaxies at their center. Using the observed Si/Fe ratio, the cumulative metal-mass-to-light ratios at 0.5 r 180 are compared with theoretical expectations.

Supernovae contributions to metals in intra-cluster medium observed with Suzaku AIP Conf.On the halo neutron star origin of the gamma-ray bursts: Origin of the halo neutron stars and metal enrichment of the intracluster medium AIP Conf.Abstract. We derived radial abundance profiles of O, Mg, Si, S and Fe in the intracluster medium (ICM) of several clusters and groups of galaxies up to about 0.3 r 180 with Suzaku and those of Fe in 28 nearby brightest clusters of galaxies up to 0.3-0.5 r 180 with XMM. Within 0.05 r 180 , Fe abundance scatters from 0.5 to 1 solar. The scatter may be caused by a difference in recent metal supplies with supernovae Ia and stellar mass loss from cD galaxies. In these regions and also in ISM in giant elliptical galaxies, the abundance patterns of O, Mg, Si, S and Fe are close to the solar ratio adopting the new solar abundance defined by Lodders [1]. At 0.1-0.5 r 180 , relaxed clusters with a cD galaxy at their X-ray peak have flat Fe abundance profiles at 0.4-0.5 solar, with a small scatter. In these clusters, the ratio of Fe mass in the ICM to the light from galaxies have similar profiles, and increases toward outer regions. In addition, several systems show a hint of enhancement of O/Fe and Mg/Fe ratios. These results indicate that the metal-enrichment process in these clusters has been universal, and a significant amount of Fe is synthesized at a very early stage in cluster formation. Scatter in the metal-mass-to-light ratios and similarity in the abundances in the ICM of groups and clusters of galaxies also indicate early metal synthesis.