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Evidence for a Merger-induced Shock Wave in ZwCl 0008.8+5215 with Chandra and Suzaku

Journal
Date Issued
2019
Author(s)
Di Gennaro, G.
•
van Weeren, R. J.
•
Andrade-Santos, F.
•
Akamatsu, H.
•
Randall, S. W.
•
Forman, W.
•
Kraft, R. P.
•
•
Dawson, W. A.
•
Golovich, N.
•
Jones, C.
DOI
Abstract
We present the results from new deep Chandra (∼410 ks) and Suzaku (∼180 ks) observations of the merging galaxy cluster ZwCl 0008.8+5215 (z = 0.104). Previous radio observations revealed the presence of a double radio relic located diametrically west and east of the cluster center. Using our new Chandra data, we find evidence for the presence of a shock at the location of the western relic, RW, with a Mach number {{ \mathcal M }}{SX}={1.48}-0.32+0.50 from the density jump. We also measure {{ \mathcal M }}{TX}={2.35}-0.55+0.74 and {{ \mathcal M }}{TX}={2.02}-0.47+0.74 from the temperature jump, with Chandra and Suzaku, respectively. These values are consistent with the Mach number estimate from a previous study of the radio spectral index, under the assumption of diffusive shock acceleration ({{ \mathcal M }}RW}={2.4}-0.2+0.4). Interestingly, the western radio relic does not entirely trace the X-ray shock. A possible explanation is that the relic traces fossil plasma from nearby radio galaxies that is reaccelerated at the shock. For the eastern relic we do not detect an X-ray surface brightness discontinuity, despite the fact that radio observations suggest a shock with {{ \mathcal M }}RE}={2.2}-0.1+0.2. The low surface brightness and reduced integration time for this region might have prevented the detection. The Chandra surface brightness profile suggests { \mathcal M }≲ 1.5, while the Suzaku temperature measurements found {{ \mathcal M }}{TX}={1.54}-0.47+0.65. Finally, we also detect a merger-induced cold front on the western side of the cluster, behind the shock that traces the western relic.
Volume
873
Issue
1
Start page
64
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2019ApJ...873...64D
Rights
open.access
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