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A distant radio mini-halo in the phoenix galaxy cluster

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Authors
Van Weeren, R.
Intema, Hubertus
Lal, D.
Andrade-Santos, F.
Brüggen, M.
De Gasperin, F.
Forman, W.
Hoeft, M.
Jones, C.
Nuza, S.
Röttgering, H.
Stroe, A.
Date
2014
Type
Journal Article

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Van Weeren, R. and Intema, H. and Lal, D. and Andrade-Santos, F. and Brüggen, M. and De Gasperin, F. and Forman, W. et al. 2014. A distant radio mini-halo in the phoenix galaxy cluster. Astrophysical Journal Letters. 786 (2): Article ID L17.
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Astrophysical Journal Letters
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This is an author-created, un-copy edited version of an article accepted for publication in Astrophysical Journal. The publisher is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at 10.1088/2041-8205/786/2/L17.

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Abstract

We report the discovery of extended radio emission in the Phoenix cluster (SPT-CL J2344-4243, z = 0.596) with the Giant Metrewave Radio Telescope (GMRT) at 610 MHz. The diffuse emission extends over a region of at least 400-500 kpc and surrounds the central radio source of the Brightest Cluster Galaxy, but does not appear to be directly associated with it. We classify the diffuse emission as a radio mini-halo, making it the currently most distant mini-halo known. Radio mini-halos have been explained by synchrotron emitting particles re-accelerated via turbulence, possibly induced by gas sloshing generated from a minor merger event. Chandra observations show a non-concentric X-ray surface brightness distribution, which is consistent with this sloshing interpretation. The mini-halo has a flux density of 17 ± 5 mJy, resulting in a 1.4 GHz radio power of (10.4 ± 3.5) × 1024 W Hz-1. The combined cluster emission, which includes the central compact radio source, is also detected in a shallow GMRT 156 MHz observation and together with the 610 MHz data we compute a spectral index of-0.84 ± 0.12 for the overall cluster radio emission. Given that mini-halos typically have steeper radio spectra than cluster radio galaxies, this spectral index should be taken as an upper limit for the mini-halo. © 2014. The American Astronomical Society. All rights reserved.