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Register a new userSuzaku Observations of the cluster of galaxies Abell 2052
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The results from Suzaku XIS observations of the relaxed cluster of galaxies Abell2052 are presented. Offset pointing data are used to estimate the Galactic foreground emission in the direction to the cluster. Significant soft X-ray excess emission above this foreground, the intra-cluster medium emission, and other background components is confirmed and resolved spectroscopically and radially. This excess can be described either by (a) local variations of known Galactic emission components or (b) an additional thermal component with temperature of about 0.2 keV, possibly associated with the cluster. The radial temperature and metal abundance profiles of the intra-cluster medium are measured within sim 20 in radius (about 60% of the virial radius) from the cluster center . The temperature drops radially to 0.5-0.6 of the peak value at a radius of sim 15. The gas-mass-weighted metal abundance averaged over the observed region is found to be 0.21 +- 0.05 times solar.
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We present an analysis of the Chandra X-ray observation of Abell 2052, including large scale properties of the cluster as well as the central region which includes the bright radio source, 3C 317. We present temperature and abundance profiles using both projected and deprojected spectral analyses. The cluster shows the cooling flow signatures of excess surface brightness above a beta- model at the cluster center, and a temperature decline into the center of the cluster. The heavy element abundances initially increase into the center, but decline within 30 arcsec. Temperature and abundance maps show that the X-ray bright shells surrounding the radio source are the coolest and least abundant regions in the cluster. The mass-deposition rate in the cooling flow is 26 < Mdot < 42 Msun/yr. This rate is ~ a factor of three lower than the rates found with previous X-ray observatories. Based on a stellar population analysis using imaging and spectra at wavelengths spanning the far UV to the NIR, we find a star formation rate of 0.6 Msun/yr within a 3 arcsec radius of the nucleus of the central cluster galaxy. Total and gas mass profiles for the cluster are also determined. We investigate additional sources of pressure in the X-ray holes formed by the radio source, and limit the temperature of any hot, diffuse, thermal component which provides the bulk of the pressure in the holes to kT > 20 keV. We calculate the magnetic field in the bright-shell region and find B ~ 11 muG. The current luminosity of the central AGN is L_X = 7.9 x 10^41 erg/s, and its spectrum is well-fitted by a power-law model with no excess absorption above the Galactic value. The energy output from several radio outbursts, occurring episodically over the lifetime of the cluster, may be sufficient to offset the cooling flow near the center. (Abridged)
We report Suzaku observations of the galaxy cluster Abell 1795 that extend to r_200 ~ 2 Mpc, the radius within which the mean cluster mass density is 200 times the cosmic critical density. These observations are the first to probe the state of the intracluster medium in this object at r > 1.3 Mpc. We sample two disjoint sectors in the cluster outskirts (1.3 < r < 1.9 Mpc) and detect X-ray emission in only one of them to a limiting (3-sigma) soft X-ray surface brightness of B(0.5-2 keV) = 1.8 x 10^-12 erg s^-1 cm^-2 deg^-2, a level less than 20% of the cosmic X-ray background brightness. We trace the run of temperature with radius at r > 0.4 Mpc and find that it falls relatively rapidly (T ~ r^-0.9), reaching a value about one third of its peak at the largest radius we can measure it. Assuming the intracluster medium is in hydrostatic equilibrium and is polytropic, we find a polytropic index of 1.3 +0.3-0.2 and we estimate a mass of 4.1 +0.5-0.3 x 10^14 M_solar within 1.3 Mpc, somewhat (2.7-sigma) lower than that reported by previous observers. However, our observations provide evidence for departure from hydrostatic equilibrium at radii as small as r ~ 1.3 Mpc ~ r_500 in this apparently regular and symmetrical cluster.
We present analysis results for a nearby galaxy cluster Abell 1631 at $z~=~0.046$ using the X-ray observatory Suzaku. This cluster is categorized as a low X-ray surface brightness cluster. To study the dynamical state of the cluster, we conduct four-pointed Suzaku observations and investigate physical properties of the Mpc-scale hot gas associated with the A1631 cluster for the first time. Unlike relaxed clusters, the X-ray image shows no strong peak at the center and an irregular morphology. We perform spectral analysis and investigate the radial profiles of the gas temperature, density, and entropy out to approximately 1.5~Mpc in the east, north, west, and south directions by combining with the XMM-Newton data archive. The measured gas density in the central region is relatively low (${rm a~few} times~10^{-4}~{rm cm^{-3}}$) at the given temperature ($sim2.9~{rm keV}$) compared with X-ray-selected clusters. The entropy profile and value within the central region ($r<0.1~r_{200}$) are found to be flatter and higher ($gtrsim400~ {rm keV~cm}^2$). The observed bolometric luminosity is approximately three times lower than that expected from the luminosity-temperature relation in previous studies for relaxed clusters. These features are also observed in another low surface brightness cluster, Abell 76. The spatial distributions of galaxies and the hot gas appear to be different. The X-ray luminosity is relatively lower than that expected from the velocity dispersion. A post-merger scenario may explain the observed results.
The results of Suzaku observations of the outskirts of Abell 3395 including a large-scale structure filament toward Abell 3391 are presented. We measured temperature and abundance distributions from the southern outskirt of Abell 3395 to the north at the virial radius, where a filament structure has been found in the former X-ray and Sunyaev-Zeldovich effect observations between Abell 3391 and 3395. The overall temperature structure is consistent with the universal profile proposed by Okabe et al.(2014) for relaxed clusters except for the filament region. A hint of the ICM heating is found between the two clusters, which might be due to the interaction of them in the early phase of a cluster merger. Although we obtained relatively low metal abundance of $Z=0.169^{+0.164+0.009+0.018 }_{-0.150-0.004-0.015 }$ solar, where the first, second, and third errors are statistical, cosmic X-ray background systematic, and non X-ray background systematic, respectively, at the virial radius in the filament, our results are still consistent with the former results of other clusters ($Z sim 0.3$ solar) within errors. Therefore, our results are also consistent with the early enrichment scenario. We estimated Compton $y$ parameters only from X-ray results in the region between Abell 3391 and 3395 assuming a simple geometry. They are smaller than the previous SZ results with Planck satellite. The difference could be attributed to a more elaborate geometry such as a filament inclined to the line-of-sight direction, or underestimation of the X-ray temperature because of the unresolved multi-temperature structures or undetected hot X-ray emission of the shock heated gas.
To investigate the present situation of the merging in the southern outer region of Abell 85, we carried out long (~100 ks) observations with Suzaku, and produced an X-ray hardness ratio map. We found a high hardness ratio peak in the east side of a subcluster located in the south of the cluster; an X-ray spectrum of the region including this peak indicates a high temperature of ~8.5 keV. This hot spot has not been reported so far. We consider that this hot spot is a postshock region produced by the infall of the subcluster from the southwest. By using the Rankine--Hugoniot jump conditions for shocks, the Mach number and the infall velocity of the subcluster are obtained as 1.5 +/- 0.2 and 1950^{+290}_{-280} km s^{-1}, respectively, in the case of merging with the subcluster from the southwest direction. By using the redshift difference between the A 85 and the subcluster obtained from optical observations, the angle between the line of sight and the direction of the motion of the subcluster is estimated to be 75^{+7}_{-8} degrees. We estimate the kinetic energy of the subcluster and the energy used for intracluster medium (ICM) heating to be ~10^{63} and lesssim 8 times 10^{60} erg, respectively. This shows that the deceleration of the subcluster by ICM heating has been negligibly small.
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