First evidence of diffuse ultra-steep-spectrum radio emission surrounding the cool core of a cluster
Date Issued
2018
Author(s)
Savini, F.
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Brüggen, M.
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van Weeren, R.
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Intema, H.
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Shimwell, T.
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Wilber, A.
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Rafferty, D.
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Giacintucci, S.
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Cuciti, V.
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Röttgering, H.
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Hoeft, M.
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White, G.
Abstract
Diffuse synchrotron radio emission from cosmic ray electrons is observed at the centre of a number of galaxy clusters. These sources can be classified either as giant radio haloes, which occur in merging clusters, or as mini haloes, which are found only in cool-core clusters. In this paper, we present the first discovery of a cool-core cluster with an associated mini halo that also shows ultra-steep-spectrum emission extending well beyond the core that resembles radio halo emission. The large-scale component is discovered thanks to LOFAR observations at 144 MHz. We also analyse GMRT observations at 610 MHz to characterize the spectrum of the radio emission. An X-ray analysis reveals that the cluster is slightly disturbed, and we suggest that the steep-spectrum radio emission outside the core could be produced by a minor merger that powers electron re-acceleration without disrupting the cool core. This discovery suggests that, under particular circumstances, both a mini halo and giant halo could co-exist in a single cluster, opening new perspectives for particle acceleration mechanisms in galaxy clusters.
Volume
478
Issue
2
Start page
2234
Issn Identifier
0035-8711
Ads BibCode
2018MNRAS.478.2234S
Rights
open.access
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