Chandra and XMM-Newton observations of A2256: cold fronts, merger shocks, and constraint on the IC emission

We present the results of deep Chandra and XMM-Newton observations of a complex merging galaxy cluster Abell 2256 (A2256) that hosts a spectacular radio relic (RR). The temperature and metallicity maps show clear evidence of a merger between the western subcluster (SC) and the primary cluster (PC)....

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Published in:arXiv.org 2020-08
Main Authors: Ge, Chong, Ruo-Yu, Liu, Sun, Ming, Yu, Heng, Rudnick, Lawrence, Eilek, Jean, Frazer, Owen, Dasadia, Sarthak, Rossetti, Mariachiara, Markevitch, Maxim, Clarke, Tracy E, Jones, Thomas W, Ghizzardi, Simona, Venturi, Tiziana, Finoguenov, Alexis, Eckert, Dominique
Format: Article
Language:English
Subjects:
Cold fronts
Galactic clusters
Galaxies
Metallicity
Power law
Radio
Shock fronts
Stellar kinematics
Substructures
Surface brightness
XMM (spacecraft)
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Summary:We present the results of deep Chandra and XMM-Newton observations of a complex merging galaxy cluster Abell 2256 (A2256) that hosts a spectacular radio relic (RR). The temperature and metallicity maps show clear evidence of a merger between the western subcluster (SC) and the primary cluster (PC). We detect five X-ray surface brightness edges. Three of them near the cluster center are cold fronts (CFs): CF1 is associated with the infalling SC; CF2 is located in the east of the PC; and CF3 is to the west of the PC core. The other two edges at cluster outskirts are shock fronts (SFs): SF1 near the RR in the NW has Mach numbers derived from the temperature and the density jumps, respectively, of \(M_T=1.62\pm0.12\) and \(M_\rho=1.23\pm0.06\); SF2 in the SE has \(M_T=1.54\pm0.05\) and \(M_\rho=1.16\pm0.13\). In the region of the RR, there is no evidence for the correlation between X-ray and radio substructures, from which we estimate an upper limit for the inverse-Compton emission, and therefore set a lower limit on the magnetic field (\(\sim\) 450 kpc from PC center) of \(B>1.0\ \mu\)G for a single power-law electron spectrum or \(B>0.4\ \mu\)G for a broken power-law electron spectrum. We propose a merger scenario including a PC, an SC, and a group. Our merger scenario accounts for the X-ray edges, diffuse radio features, and galaxy kinematics, as well as projection effects.
ISSN:2331-8422
DOI:10.48550/arxiv.2005.10838