Suzaku Observations of Abell 1795: Cluster Emission to R_200

TL;DR

This study uses Suzaku X-ray observations to explore the outer regions of galaxy cluster Abell 1795, revealing temperature decline, mass estimates, and signs of departure from hydrostatic equilibrium at large radii.

Contribution

First Suzaku measurements of Abell 1795's intracluster medium beyond 1.3 Mpc, providing new insights into cluster outskirts and hydrostatic equilibrium assumptions.

Findings

Temperature decreases with radius, reaching one-third of its peak at the outermost measured point.

Estimated cluster mass within 1.3 Mpc is lower than previous reports.

Evidence of departure from hydrostatic equilibrium at large radii.

Abstract

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.