Discovery of a giant radio halo in a new Planck galaxy cluster PLCKG171.9-40.7

TL;DR

This paper reports the discovery of a giant radio halo in a newly identified, hot, X-ray luminous galaxy cluster detected by Planck, using radio and X-ray observations, marking the first such detection in a Planck cluster.

Contribution

The paper presents the first discovery of a giant radio halo in a Planck-detected galaxy cluster, expanding knowledge of radio emissions in newly identified clusters.

Findings

Radio halo extent ~1 Mpc

Radio power ~5x10^24 W/Hz at 1.4 GHz

Steep spectral index alpha~1.8

Abstract

We report the discovery of a giant radio halo in a new, hot, X-ray luminous galaxy cluster recently found by Planck, PLCKG171.9-40.7. The radio halo was found using Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz, and in the 1.4 GHz data from a NRAO Very Large Array Sky Survey pointing that we have reanalyzed. The diffuse radio emission is coincident with the cluster X-ray emission, has an extent of ~1 Mpc and a radio power of ~5x 10^24 W/Hz at 1.4 GHz. Its integrated radio spectrum has a slope of alpha~1.8 between 235 MHz and 1.4 GHz, steeper than that of a typical giant halo. The analysis of the archival XMM-Newton X-ray data shows that the cluster is hot (~10 keV) and disturbed, consistent with X-ray selected clusters hosting radio halos. This is the first giant radio halo discovered in one of the new clusters found by Planck.