Volume 627, July 2019
|Number of page(s)||14|
|Published online||22 July 2019|
Signatures from a merging galaxy cluster and its AGN population: LOFAR observations of Abell 1682
Jodrell Bank Centre for Astrophysics, School of Physics & Astronomy, University of Manchester, M13 9PL Manchester, UK
2 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
3 ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands
4 Dipartimento di Fisica e Astronomia, Universitá di Bologna, Via P. Gobetti 93/2, 40129 Bologna, Italy
5 INAF-IRA, Via P. Gobetti 101, 40129 Bologna, Italy
6 CSIRO Astronomy and Space Science, 26 Dick Perry Avenue, Kensington, WA 6151, Australia
7 Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
8 Hamburger Sternwarte, Universitat Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
9 Chalmers University of Technology, Dept. of Space, Earth and Environment, Onsala Space Observatory, 439 92 Onsala, Sweden
10 Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
11 Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany
Accepted: 12 June 2019
We present LOFAR data from 110–180 MHz of the merging galaxy cluster Abell 1682, alongside archival optical, radio, and X-ray data. Our images of 6 arcsec in resolution at low frequencies reveal new structures associated with numerous radio galaxies in the cluster. At a resolution of 20 arcsec we see diffuse emission throughout the cluster over hundreds of kiloparsecs, indicating particle acceleration mechanisms are in play as a result of the cluster merger event and powerful active galactic nuclei. We show that a significant part of the cluster emission is from an old radio galaxy with very steep spectrum emission (having a spectral index of α < −2.5). Furthermore, we identify a new region of diffuse steep-spectrum emission (α < −1.1) as a candidate for a radio halo which is co-spatial with the centre of the cluster merger. We suggest its origin as a population of old and mildly relativistic electrons left over from radio galaxies throughout the cluster which have been re-accelerated to higher energies by shocks and turbulence induced by the cluster merger event. We also note the discovery of six new giant radio galaxies in the vicinity of Abell 1682.
Key words: galaxies: clusters: intracluster medium / galaxies: halos / radiation mechanisms: non-thermal / galaxies: jets / radio continuum: galaxies / quasars: supermassive black holes
© ESO 2019
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