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Published February 1, 2017 | Published + Submitted
Journal Article Open

Chandra and JVLA Observations of HST Frontier Fields Cluster MACS J0717.5+3745


To investigate the relationship between thermal and non-thermal components in merger galaxy clusters, we present deep JVLA and Chandra observations of the HST Frontier Fields cluster MACS J0717.5+3745. The Chandra image shows a complex merger event, with at least four components belonging to different merging subclusters. Northwest of the cluster, ~0.7 Mpc from the center, there is a ram-pressure-stripped core that appears to have traversed the densest parts of the cluster after entering the intracluster medium (ICM) from the direction of a galaxy filament to the southeast. We detect a density discontinuity north-northeast of this core, which we speculate is associated with a cold front. Our radio images reveal new details for the complex radio relic and radio halo in this cluster. In addition, we discover several new filamentary radio sources with sizes of 100–300 kpc. A few of these seem to be connected to the main radio relic, while others are either embedded within the radio halo or projected onto it. A narrow-angled-tailed (NAT) radio galaxy, a cluster member, is located at the center of the radio relic. The steep spectrum tails of this active galactic nucleus lead into the large radio relic where the radio spectrum flattens again. This morphological connection between the NAT radio galaxy and relic provides evidence for re-acceleration (revival) of fossil electrons. The presence of hot ≳20 keV ICM gas detected by Chandra near the relic location provides additional support for this re-acceleration scenario.

Additional Information

© 2017 The American Astronomical Society. Received 2016 November 15; revised 2016 December 22; accepted 2016 December 24; published 2017 January 31. We thank the anonymous referee for useful comments. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Support for this work was provided by the National Aeronautics and Space Administration through Chandra Award Number GO4-15129X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060. R.J.W. is supported by a Clay Fellowship awarded by the Harvard-Smithsonian Center for Astrophysics. M.B. acknowledges support by the research group FOR 1254 funded by the Deutsche Forschungsgemeinschaft: "Magnetization of interstellar and intergalactic media: the prospects of low-frequency radio observations." W.R.F., C.J., and F.A.-S. acknowledge support from the Smithsonian Institution. E.R. acknowledges a Visiting Scientist Fellowship of the Smithsonian Astrophysical Observatory, and the hospitality of the Center for Astrophysics in Cambridge. G.A.O. acknowledges support by NASA through a Hubble Fellowship grant HST-HF2-51345.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. F.A.-S. acknowledges support from Chandra grant GO3-14131X. A.Z. is supported by NASA through Hubble Fellowship grant HST-HF2-51334.001-A awarded by STScI. This research was performed while T.M. held a National Research Council Research Associateship Award at the Naval Research Laboratory (NRL). Basic research in radio astronomy at NRL by T.M. and T.E.C. is supported by 6.1 Base funding. M.D. acknowledges the support of STScI grant 12065.007-A. P.E.J.N. was partially supported by NASA contract NAS8-03060. Part of this work performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344. Part of the reported results are based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-26555. This work utilizes gravitational lensing models produced by PIs Bradač Ebeling, Merten & Zitrin, Sharon, and Williams funded as part of the HST Frontier Fields program conducted by STScI. The lens models were obtained from the Mikulski Archive for Space Telescopes (MAST). Facilities: VLA - Very Large Array, CXO - Chandra X-ray Observatory satellite.

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Published - van_Weeren_2017_ApJ_835_197.pdf

Submitted - 1701.04096v1.pdf


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