Radio halos in SZ-selected clusters of galaxies: the making of a halo?

TL;DR

This study uses SZ-selected galaxy clusters to discover new radio halos and peculiar emissions, revealing diverse properties and challenging existing correlations, thus advancing understanding of cluster mergers and non-thermal phenomena.

Contribution

It presents new radio halo detections in SZ-selected clusters, including the first in the 'upper-limit' radio-X-ray region, expanding knowledge of cluster radio emissions.

Findings

Discovered a radio halo in RXCJ0949.8+1708.

Identified a radio halo plus relic in Abell 1443.

Detected low-power radio emission in CIZA J1938.3+5409.

Abstract

Radio halos are synchrotron radio sources detected in some massive galaxy clusters. Their Mpc-size indicates that (re)acceleration processes are taking place in the host cluster. X-ray catalogues of galaxy clusters have been used in the past to search for radio halos and to understand their connection with cluster-cluster mergers and with the thermal component of the intra-cluster medium. More recently, the Sunyaev-Zel'dovich effect has been proven to be a better route to search for massive clusters in a wider redshift range. With the aim of discovering new radio halos and understanding their connection with cluster-cluster mergers, we have selected from the Planck Early source catalog the most massive clusters, and we have observed with the Giant Metrewave Radio Telescope at 323 MHz those objects for which deep observations were not available. We have discovered new peculiar radio emission in three of the observed clusters finding: (i) a radio halo in the cluster RXCJ0949.8+1708; (ii) extended emission in Abell 1443 that we classify as a radio halo plus a radio relic, with a bright filament embedded in the radio halo; (iii) low-power radio emission is found in CIZA J1938.3+5409 which is ten times below the radio - X-ray correlation, and represents the first direct detection of the radio emission in the "upper-limit" region of the radio - X-ray diagram. We discuss the properties of these new radio halos in the framework of theoretical models for the radio emission.