A DISTANT RADIO MINI-HALO IN THE PHOENIX GALAXY CLUSTER

作者：van Weeren R J^*; Intema H T; Lal D V; Andrade Santos F; Brueggen M; de Gasperin F; Forman W R; Hoeft M; Jones C; Nuza S E; Rottgering H J A; Stroe A

来源：Astrophysical Journal Letters, 2014, 786(2): L17.

DOI：10.1088/2041-8205/786/2/L17

• galaxies: clusters: individual (SPT-CL J2344-4243)
• galaxies: clusters: intracluster medium
• large-scale structure of universe
• radiation mechanisms: non-thermal
• X-rays: galaxies: clusters

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) x 10(24) WHz(-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.

• 出版日期2014-5-10