Deep Chandra observations of merging galaxy cluster ZwCl 2341+0000
Journal
Date Issued
2021
Author(s)
Zhang, X.
•
Simionescu, A.
•
•
van Weeren, R. J.
•
Intema, H. T.
•
Akamatsu, H.
•
de Plaa, J.
•
Kaastra, J. S.
•
•
Brüggen, M.
•
ZuHone, J.
•
Ichinohe, Y.
Description
Acknowledgements. We thank the anonymous referee for useful comments and
suggestions that helped improve this paper. X.Z. acknowledges support from
Chinese Scholarship Council (CSC). A.S. is supported by the Women In Science Excel (WISE) programme of the Netherlands Organisation for Scientific
Research (NWO), and acknowledges the World Premier Research Center Initiative (WPI) and the Kavli IPMU for the continued hospitality. SRON Netherlands
Institute for Space Research is supported financially by NWO. R.J.vW. acknowledges support from the ERC Starting Grant ClusterWeb 804208. C.S. and A.B.
acknowledge support from ERC-Stg DRANOEL n. 714245. This research has
made use of data obtained from the Chandra Data Archive and the Chandra
Source Catalog, and software provided by the Chandra X-ray Center (CXC) in
the application package CIAO. The National Radio Astronomy Observatory is a
facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We thank the staff of the GMRT who
have made these observations possible. The GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. This
work made use of data from the Galaxy Cluster Merger Catalog. This research
made use of Astropy (http://www.astropy.org), a community-developed
core Python package for Astronomy (Astropy Collaboration 2013, 2018).
Abstract
Context. Knowledge of X-ray shock and radio relic connection in merging galaxy clusters has been greatly extended in terms of both observation and theory over the last decade. ZwCl 2341+0000 is a double-relic merging galaxy cluster; previous studies have shown that half of the southern relic is associated with an X-ray surface brightness discontinuity, while the other half not. The discontinuity was believed to be a shock front. Therefore, it is a mysterious case of an only partial shock-relic connection.
Aims: By using the 206.5 ks deep Chandra observations, we aim to investigate the nature of the southern surface brightness discontinuity. Meanwhile, we aim to explore new morphological and thermodynamical features.
Methods: We perform both imaging and spectroscopic analyses to investigate the morphological and thermodynamical properties of the cluster. In addition to the X-ray data, we utilize the GMRT 325 MHz image and JVLA 1.5 GHz and 3.0 GHz images to compute radio spectral index maps.
Results: Surface brightness profile fitting and the temperature profile suggest that the previously reported southern surface brightness discontinuity is better described as a sharp change in slope or as a kink. This kink is likely contributed by the disrupted core of the southern subcluster. The radio spectral index maps show spectral flattening at the south-eastern edge of the southern relic, suggesting that the location of the shock front is 640 kpc away from the kink, where the X-ray emission is too faint to detect a surface brightness discontinuity. We update the radio shock Mach number to be ℳradio, S = 2.2 ± 0.1 and ℳradio, N = 2.4 ± 0.4 for the southern and northern radio relics based on the injection spectral indices. We also put a 3σ lower limit on the X-ray Mach number of the southern shock to be ℳX-ray, S > 1.6. Meanwhile, the deep observations reveal that the northern subcluster is in a perfect cone shape, with a ∼400 kpc linear cold front on each side. This type of conic subcluster has been predicted by simulations but is observed here for the first time. It represents a transition stage between a blunt-body cold front and a slingshot cold front. Strikingly, we found a 400 kpc long gas trail attached to the apex of the cone, which could be due to the gas stripping. In addition, an over-pressured hot region is found in the south-western flank of the cluster.
Aims: By using the 206.5 ks deep Chandra observations, we aim to investigate the nature of the southern surface brightness discontinuity. Meanwhile, we aim to explore new morphological and thermodynamical features.
Methods: We perform both imaging and spectroscopic analyses to investigate the morphological and thermodynamical properties of the cluster. In addition to the X-ray data, we utilize the GMRT 325 MHz image and JVLA 1.5 GHz and 3.0 GHz images to compute radio spectral index maps.
Results: Surface brightness profile fitting and the temperature profile suggest that the previously reported southern surface brightness discontinuity is better described as a sharp change in slope or as a kink. This kink is likely contributed by the disrupted core of the southern subcluster. The radio spectral index maps show spectral flattening at the south-eastern edge of the southern relic, suggesting that the location of the shock front is 640 kpc away from the kink, where the X-ray emission is too faint to detect a surface brightness discontinuity. We update the radio shock Mach number to be ℳradio, S = 2.2 ± 0.1 and ℳradio, N = 2.4 ± 0.4 for the southern and northern radio relics based on the injection spectral indices. We also put a 3σ lower limit on the X-ray Mach number of the southern shock to be ℳX-ray, S > 1.6. Meanwhile, the deep observations reveal that the northern subcluster is in a perfect cone shape, with a ∼400 kpc linear cold front on each side. This type of conic subcluster has been predicted by simulations but is observed here for the first time. It represents a transition stage between a blunt-body cold front and a slingshot cold front. Strikingly, we found a 400 kpc long gas trail attached to the apex of the cone, which could be due to the gas stripping. In addition, an over-pressured hot region is found in the south-western flank of the cluster.
Volume
656
Issue
A59
Start page
1
Issn Identifier
0004-6361
Ads BibCode
2021A&A...656A..59Z
Rights
open.access
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