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.
Categories: astro-ph.CO astro-ph.GA