The Entire Virial Radius of the Fossil Cluster RX J1159+5531: I. Gas Properties
Journal
Date Issued
2015
Author(s)
Description
We thank the anonymous referee for a careful reading of the manuscript. We are grateful to Philip Humphrey for early contributions to this project, especially for developing initial versions of software for the data analysis and mass modeling. D.A.B. and Y.S. gratefully acknowledge partial support from the National Aeronautics and Space Administration under Grant No. NNX13AF14G issued through the Astrophysics Data Analysis Program. Partial support for this work was also provided by NASA through Chandra Award Number GO2-13159X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. F.G. acknowledges the financial contribution from contract PRIN INAF 2012 (“A unique dataset to address the most compelling open questions about X-ray galaxy clusters”) and the contract ASI INAF NuSTAR I/037/12/0.
Abstract
Previous analysis of the fossil-group/cluster RX J1159+5531 with X-ray observations from a central Chandra pointing and an offset-north Suzaku pointing indicate a radial intracluster medium (ICM) entropy profile at the virial radius (Rvir) consistent with predictions from gravity-only cosmological simulations, in contrast to other cool-core clusters. To examine the generality of these results, we present three new Suzaku observations that, in conjunction with the north pointing, provide complete azimuthal coverage out to Rvir. With two new Chandra ACIS-I observations overlapping the north Suzaku pointing, we have resolved ≳50% of the cosmic X-ray background there. We present radial profiles of the ICM density, temperature, entropy, and pressure obtained for each of the four directions. We measure only modest azimuthal scatter in the ICM properties at R200 between the Suzaku pointings: 7.6% in temperature and 8.6% in density, while the systematic errors can be significant. The temperature scatter, in particular, is lower than that studied at R200 for a small number of other clusters observed with Suzaku. These azimuthal measurements verify that RX J1159+5531 is a regular, highly relaxed system. The well-behaved entropy profiles we have measured for RX J1159+5531 disfavor the weakening of the accretion shock as an explanation of the entropy flattening found in other cool-core clusters but is consistent with other explanations such as gas clumping, electron-ion non-equilibrium, non-thermal pressure support, and cosmic-ray acceleration. Finally, we mention that the large-scale galaxy density distribution of RX J1159+5531 seems to have little impact on its gas properties near Rvir.
Volume
805
Issue
2
Start page
104
Issn Identifier
0004-637X
Ads BibCode
2015ApJ...805..104S
Rights
open.access
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