LOFAR discovery of a radio halo in the high-redshift galaxy cluster PSZ2 G099.86+58.45

Abstract

In this Letter, we report the discovery of a radio halo in the high-redshift galaxy cluster PSZ2 G099.86+58.45 ($z=0.616$) with the LOw Frequency ARray (LOFAR) at 120-168 MHz. This is one of the most distant radio halos discovered so far. The diffuse emission extends over $\sim$ 1 Mpc and has a morphology similar to that of the X-ray emission as revealed by XMM-Newton data. The halo is very faint at higher frequencies and is barely detected by follow-up 1-2 GHz Karl G.~Jansky Very Large Array (JVLA) observations, which enable us to constrain the radio spectral index to be $\alpha \le 1.5-1.6$, i.e.; with properties between canonical and ultra-steep spectrum radio halos. Radio halos are currently explained as synchrotron radiation from relativistic electrons that are re-accelerated in the intra-cluster medium (ICM) by turbulence driven by energetic mergers. We show that in such a framework radio halos are expected to be relatively common at $\sim 150$ MHz ($\sim 30-60\%$) in clusters with mass and redshift similar to PSZ2 G099.86+58.45; however, at least 2/3 of these radio halos should have steep spectrum and thus be very faint above $\sim 1$ GHz frequencies. Furthermore, since the luminosity of radio halos at high redshift depends strongly on the magnetic field strength in the hosting clusters, future LOFAR observations will also provide vital information on the origin and amplification of magnetic fields in galaxy clusters.

6 pages, 3 figures, accepted (2019, July 17) for publication in ApJ Letter

References in corpus (13)

• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release
• Diffuse Radio Emission from Galaxy Clusters
• The non-coplanar baselines effect in radio interferometry: The W-Projection algorithm
• A low-frequency radio halo associated with a cluster of galaxies
• GMRT Radio Halo Survey in galaxy clusters at z = 0.2 -- 0.4. II.The eBCS clusters and analysis of the complete sample
• Radio interferometric gain calibration as a complex optimization problem
• GMRT Radio Halo Survey in galaxy clusters at z = 0.2 -- 0.4 I.The REFLEX sub--sample
• Statistics of Giant Radio Halos from Electron Reacceleration Models
• Resolved magnetic dynamo action in the simulated intracluster medium
• Non-linear Kalman filters for calibration in radio interferometry
• The Extended GMRT Radio Halo Survey II: Further results and analysis of the full sample
• LOFAR discovery of an ultra-steep radio halo and giant head-tail radio galaxy in Abell 1132

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