Watching Clusters Form: Suzaku Observations of the Outskirts of Abell 1795
Abstract
The outskirts of galaxy clusters, beyond r500, remain relatively unexplored territory and yet are vital to our understanding of cluster growth, structure, and mass. Recent studies taking advantage of the Suzaku X-ray Observatory's stable background and substantial effective area have successfully detected ICM emission out to r200 in a handful of clusters. We here present new Suzaku observations of the nearby galaxy cluster Abell 1795 which, when combined with previous observations, comprise nine pointings for a total of 250 ksec and cover half the cluster out to r200 ( 26 arcmin). We detect cluster emission at r200 towards certain directions but not others at a difference of greater than 3-sigma, suggesting deviations from hydrostatic equilibrium in this apparently relaxed system. Combining the Suzaku data with overlapping XMM observations, we confirm the steeply dropping temperature profile derived from our previous observations and seen in other clusters, identifying significant temperature variations at r200 toward different radial directions. The low and azimuthally varying plasma temperatures could result from low-entropy material falling into the cluster near r200, as suggested by cluster formation simulations. We discuss these results in the context of cluster and structure formation, and outline a project to observe a large sample of relaxed clusters with Suzaku to determine whether such deviations are widespread.
- Publication:
-
AAS/High Energy Astrophysics Division #11
- Pub Date:
- March 2010
- Bibcode:
- 2010HEAD...11.3102M