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Title: Frontier Fields Clusters: Deep Chandra Observations of the Complex Merger MACS J1149.6+2223

The Hubble Space Telescope Frontier Fields cluster MACS J1149.6+2223 is one of the most complex merging clusters, believed to consist of four dark matter halos. Here, we present results from deep (365 ks) Chandra observations of the cluster, which reveal the most distant cold front (z = 0.544) discovered to date. In the cluster outskirts, we also detect hints of a surface brightness edge that could be the bow shock preceding the cold front. The substructure analysis of the cluster identified several components with large relative radial velocities, thus indicating that at least some collisions occur almost along the line of sight. The inclination of the mergers with respect to the plane of the sky poses significant observational challenges at X-ray wavelengths. MACS J1149.6+2223 possibly hosts a steep-spectrum radio halo. Lastly, if the steepness of the radio halo is confirmed, then the radio spectrum, combined with the relatively regular ICM morphology, could indicate that MACS J1149.6+2223 is an old merging cluster.
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  1. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Univ. of California, Davis, CA (United States)
  4. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Johns Hopkins Univ., Baltimore, MD (United States). Department of Physics and Astronomy
  5. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Univ. of Western Australia, Crawley WA (Australia). International Centre for Radio Astronomy Research (ICRAR)
  6. Dublin Inst. for Advanced Studies, Dublin (Ireland). Astronomy and Astrophysics Section; Univ. of Hull, Hull (United Kingdom). E. A. Milne Centre for Astrophysics, Dept. of Physics and Mathematics
  7. California Inst. of Technology (CalTech), Pasadena, CA (United States). Cahill Center for Astronomy and Astrophysics
  8. Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences
  9. Academia Sinica, Taipei (Taiwan). Inst. of Astronomy and Astrophysics
  10. Naval Research Lab. (NRL), Washington, DC (United States)
  11. Univ. of Hamburg (Germany). Hamburger Sternwarte
  12. Max Planck Society, Garching (Germany). Max Planck Inst. for Astrophysics; Space Research Inst., Moscow (Russia)
  13. Univ. of Oxford (United Kingdom). Dept. of Physics
  14. Michigan State Univ., East Lansing, MI (United States). Dept. of Physics and Astronomy
  15. National Radio Astronomy Observatory, Charlottesville, VA (United States)
  16. Univ. of Ferrara (Italy). Dept. of Physics and Earth Science
  17. Univ. of Hawaii, Honolulu, HI (United States). Inst. for Astronomy
Publication Date:
Report Number(s):
Journal ID: ISSN 1538-4357
Grant/Contract Number:
AC52-07NA27344; HST-HF2-51345.001-A; NAS5-26555; G03-14131X; NAS8-03060; HST-HF2-51334.001-A
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 819; Journal Issue: 2; Journal ID: ISSN 1538-4357
Institute of Physics (IOP)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE; National Aeronautic and Space Administration (NASA)
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; galaxies: clusters: general; galaxies: clusters: individual (MACS J1149.6+2223); galaxies: clusters: intracluster medium
OSTI Identifier: