Evidence for a merger induced shock wave in ZwCl\,0008.8+5215 with {\it Chandra} and {\it Suzaku}

G. Di Gennaro; R. J. van Weeren; F. Andrade-Santos; H. Akamatsu; S. W. Randall; W. Forman; R. P. Kraft; G. Brunetti; W. A. Dawson; N. Golovich; C. Jones

doi:10.3847/1538-4357/ab03cd

paper

Evidence for a merger induced shock wave in ZwCl\,0008.8+5215 with {\it Chandra} and {\it Suzaku}

arXiv:1902.00235 · doi:10.3847/1538-4357/ab03cd

Abstract

We present the results from new deep {\it Chandra} ( $\sim 410$ ~ks) and {\it Suzaku} ( $\sim 180$ 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 {\it Chandra} data, we find evidence for the presence of a shock at the location of the western relic, RW, with a Mach number $M_{S_{X}} = 1.4 8_{- 0.32}^{+ 0.50}$ from the density jump. We also measure $M_{T_{X}} = 2.3 5_{- 0.55}^{+ 0.74}$ and $M_{T_{X}} = 2.0 2_{- 0.47}^{+ 0.74}$ from the temperature jump, with {\it Chandra} and {\it 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 ( $M_{RW} = 2. 4_{- 0.2}^{+ 0.4}$ ). 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 which is re-accelerated 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 $M_{RE} = 2. 2_{- 0.1}^{+ 0.2}$ . The low surface brightness and reduced integration time for this region might have prevented the detection. {\it Chandra} surface brightness profile suggests $M ≲ 1.5$ , while {\it Suzaku} temperature measurements found $M_{T_{X}} = 1.5 4_{- 0.47}^{+ 0.65}$ . Finally, we also detect a merger induced cold front on the western side of the cluster, behind the shock that traces the western relic.

arXiv comment21 pages, 15 figures, 4 tables; accepted for publication in ApJ

Evidence for a merger induced shock wave in ZwCl\,0008.8+5215 with {\it Chandra} and {\it Suzaku}

Abstract

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