SUZAKU OBSERVATIONS OF THE OUTSKIRTS OF A1835: DEVIATION FROM HYDROSTATIC EQUILIBRIUM

We present results of four-pointing Suzaku X-ray observations (total similar to 200 ks) of the intracluster medium (ICM) in the A1835 galaxy cluster (kT similar to 8 keV, z = 0.253) out to the virial radius (r(vir) similar to 2.9 Mpc) and beyond. Faint X-ray emission from the ICM out to rvir is detected. The temperature gradually decreases with radius from similar to 8 keV in the inner region to similar 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) less than or similar to r less than or similar to 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) less than or similar to r less than or similar to 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 Wilkinson Microwave Anisotropy Probe seven-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 A1689, 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).