A KAT-7 view of a low-mass sample of galaxy clusters

TL;DR

This study uses the KAT-7 telescope to survey 14 low-mass galaxy clusters for radio halos, finding that bright radio halos are rare in such systems, thus extending understanding of their occurrence.

Contribution

First survey of low-mass galaxy clusters with KAT-7, providing new upper limits on radio halo presence and confirming their rarity in less massive clusters.

Findings

Approximately 50% of clusters show no detectable radio halos.

Upper limits on radio emission are between 0.6 and 1.9 x 10^{24} W/Hz.

Bright radio halos are statistically rare in low-mass galaxy clusters.

Abstract

Radio observations over the last two decades have provided evidence that diffuse synchrotron emission in the form of megaparsec-scale radio halos in galaxy clusters is likely tracing regions of the intracluster medium where relativistic particles are accelerated during cluster mergers. In this paper we present results of a survey of 14 galaxy clusters carried out with the 7-element Karoo Array Telescope at 1.86 GHz, aimed to extend the current studies of radio halo occurrence to systems with lower masses (M$_{\rm 500} > 4\times10^{14}$ M${_\odot}$). We found upper limits at the $0.6 - 1.9 \times 10^{24}$ Watt Hz$^{-1}$ level for $\sim 50\%$ of the sample, confirming that bright radio halos in less massive galaxy clusters are statistically rare.