We present relations between X-ray luminosity and velocity dispersion (L − σ), X-ray luminosity and gas mass (L − M gas ), and cluster radius and velocity dispersion (r 500 − σ) for 62 galaxy clusters in the HIFLUGCS, an X-ray flux-limited sample minimizing bias toward any cluster morphology. Our analysis in total is based on ∼1.3 Ms of clean X-ray XMM-Newton data and 13439 cluster member galaxies with redshifts. Cool cores are among the major contributors to the scatter in the L − σ relation. When the cool-core-corrected X-ray luminosity is used the intrinsic scatter decreases to 0.27 dex. Even after the X-ray luminosity is corrected for the cool core, the scatter caused by the presence of cool cores dominates for the low-mass systems. The scatter caused by the non-cool-core clusters does not strongly depend on the mass range, and becomes dominant in the high-mass regime. The observed L − σ relation agrees with the self-similar prediction, matches that of a simulated sample with AGN feedback disregarding six clusters with <45 cluster members with spectroscopic redshifts, and shows a common trend of increasing scatter toward the low-mass end, i.e., systems with σ ≤ 500 km s −1 . A comparison of observations with simulations indicates an AGN-feedback-driven impact in the low-mass regime. The best fits to the L − M gas relations for the disturbed clusters and undisturbed clusters in the observational sample closely match those of the simulated samples with and without AGN feedback, respectively. This suggests that one main cause of the scatter is AGN activity providing feedback in different phases, e.g. during a feedback cycle. The slope and scatter in the observed r 500 − σ relation is similar to that of the simulated sample with AGN feedback except for a small offset but still within the scatter.

We present results of four-pointing Suzaku X-ray observations (total ∼200 ks) of the intracluster medium (ICM) in the Abell 1835 galaxy cluster (kT ∼ 8 keV, z = 0.253) out to the virial radius (r vir ∼ 2.9 Mpc) and beyond. Faint X-ray emission from the ICM out to r vir is detected. The temperature gradually decreases with radius from ∼8 keV in the inner region to ∼2 keV at r vir . The entropy profile is shown to flatten beyond r 500 , in disagreement with the r 1.1 dependence predicted from the accretion shock heating model. The thermal pressure profile in the range 0.3r 500 < ∼ r < ∼ r vir agrees well with that obtained from the stacked Sunyaev-Zel'dovich effect observations with the Planck satellite. The hydrostatic mass profile in the cluster outskirts (r 500 < ∼ r < ∼ r vir ) falls well short of the weak lensing one derived from Subaru/Suprime-Cam observations, showing an unphysical decrease with radius. The gas mass fraction at r vir defined with the lensing total mass agrees with the cosmic baryon fraction from the WMAP 7-year data. All these results indicate, rather than the gas-clumping effect, that the bulk of the ICM in the cluster outskirts is far from hydrostatic equilibrium and infalling matter retained some of its kinetic energy. Finally, combining with our recent Suzaku and lensing analysis of Abell 1689, a cluster of similar mass, temperature, and redshift, we show that the cluster temperature distribution in the outskirts is significantly correlated with the galaxy density field in the surrounding large-scale environment at (1-2)r vir .

We present the results of deep 140 ks Suzaku X-ray observations of the north-east (NE) radio relic of the merging galaxy cluster Abell 2255. The temperature structure of Abell 2255 is measured out to 0.9 times the virial radius (1.9 Mpc) in the NE direction for the first time. The Suzaku temperature map of the central region suggests a complex temperature distribution, which agrees with previous work. Additionally, on a larger-scale, we confirm that the temperature drops from 6 keV around the cluster center to 3 keV at the outskirts, with two discontinuities at r∼5 ′ (450 kpc) and ∼12 ′ (1100 kpc) from the cluster center. Their locations coincide with surface brightness discontinuities marginally detected in the XMM-Newton image, which indicates the presence of shock structures. From the temperature drop, we estimate the Mach numbers to be M inner ∼1.2 and, M outer ∼1.4. The first structure is most likely related to the large cluster core region (∼350-430 kpc), and its Mach number is consistent with the XMM-Newton observation (M ∼1.24: Sakelliou & Ponman 2006). Our detection of the second temperature jump, based on the Suzaku key project observation, shows the presence of a shock structure across the NE radio relic. This indicates a connection between the shock structure and the relativistic electrons that generate radio emission. Across the NE radio relic, however, we find a significantly lower temperature ratio (T 1 /T 2 ∼ 1.44 ± 0.16 corresponds to M X−ray ∼ 1.4) than the value expected from radio wavelengths, based on the standard diffusive shock acceleration mechanism (T 1 /T 2 > 3.2 or M Radio > 2.8). This may suggest that under some conditions, in particular the NE relic of A2255 case, the simple diffusive shock acceleration mechanism is unlikely to be valid, and therefore, more a sophisticated mechanism is required.