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

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 $${{ \mathcal M }}_{{S}_{X}}={1.48}_{-0.32}^{+0.50}$$ from the density jump. We also measure $${{ \mathcal M }}_{{T}_{X}}={2.35}_{-0.55}^{+0.74}$$ and $${{ \mathcal M }}_{{T}_{X}}={2.02}_{-0.47}^{+0.74}$$ 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 ($${{ \mathcal M }}_{\mathrm{RW}}={2.4}_{-0.2}^{+0.4}$$). 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 $${{ \mathcal M }}_{\mathrm{RE}}={2.2}_{-0.1}^{+0.2}$$. The low surface brightness and reduced integration time for this region might have prevented the detection. The Chandra surface brightness profile suggests $${ \mathcal M }\lesssim 1.5$$, while the Suzaku temperature measurements found $${{ \mathcal M }}_{{T}_{X}}={1.54}_{-0.47}^{+0.65}$$. Lastly, we also detect a merger-induced cold front on the western side of the cluster, behind the shock that traces the western relic.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [2];  [4]; ORCiD logo [5]; ORCiD logo [5];  [2]
  1. Leiden Univ. (Netherlands); Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  2. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  3. SRON Netherlands Inst. for Space Research, Utrecht (The Netherlands)
  4. Istituto di Radio Astronomia, INAF, Bologna (Italy)
  5. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC); National Aeronautics Space Administration (NASA)
OSTI Identifier:
1545278
Grant/Contract Number:  
AC52-07NA27344; NAS8-03060
Resource Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 873; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS

Citation Formats

Di Gennaro, G., van Weeren, R. J., Andrade-Santos, F., Akamatsu, H., Randall, S. W., Forman, W., Kraft, R. P., Brunetti, G., Dawson, W. A., Golovich, N., and Jones, C. Evidence for a Merger-induced Shock Wave in ZwCl 0008.8+5215 with Chandra and Suzaku. United States: N. p., 2019. Web. doi:10.3847/1538-4357/ab03cd.
Di Gennaro, G., van Weeren, R. J., Andrade-Santos, F., Akamatsu, H., Randall, S. W., Forman, W., Kraft, R. P., Brunetti, G., Dawson, W. A., Golovich, N., & Jones, C. Evidence for a Merger-induced Shock Wave in ZwCl 0008.8+5215 with Chandra and Suzaku. United States. doi:10.3847/1538-4357/ab03cd.
Di Gennaro, G., van Weeren, R. J., Andrade-Santos, F., Akamatsu, H., Randall, S. W., Forman, W., Kraft, R. P., Brunetti, G., Dawson, W. A., Golovich, N., and Jones, C. Tue . "Evidence for a Merger-induced Shock Wave in ZwCl 0008.8+5215 with Chandra and Suzaku". United States. doi:10.3847/1538-4357/ab03cd.
@article{osti_1545278,
title = {Evidence for a Merger-induced Shock Wave in ZwCl 0008.8+5215 with Chandra and Suzaku},
author = {Di Gennaro, G. and van Weeren, R. J. and Andrade-Santos, F. and Akamatsu, H. and Randall, S. W. and Forman, W. and Kraft, R. P. and Brunetti, G. and Dawson, W. A. and Golovich, N. and Jones, C.},
abstractNote = {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 ${{ \mathcal M }}_{{S}_{X}}={1.48}_{-0.32}^{+0.50}$ from the density jump. We also measure ${{ \mathcal M }}_{{T}_{X}}={2.35}_{-0.55}^{+0.74}$ and ${{ \mathcal M }}_{{T}_{X}}={2.02}_{-0.47}^{+0.74}$ 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 (${{ \mathcal M }}_{\mathrm{RW}}={2.4}_{-0.2}^{+0.4}$). 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 ${{ \mathcal M }}_{\mathrm{RE}}={2.2}_{-0.1}^{+0.2}$. The low surface brightness and reduced integration time for this region might have prevented the detection. The Chandra surface brightness profile suggests ${ \mathcal M }\lesssim 1.5$, while the Suzaku temperature measurements found ${{ \mathcal M }}_{{T}_{X}}={1.54}_{-0.47}^{+0.65}$. Lastly, we also detect a merger-induced cold front on the western side of the cluster, behind the shock that traces the western relic.},
doi = {10.3847/1538-4357/ab03cd},
journal = {The Astrophysical Journal (Online)},
number = 1,
volume = 873,
place = {United States},
year = {2019},
month = {3}
}

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