A KAT-7 view of a low-mass sample of galaxy clusters
  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. 
G. Bernardi, T. Venturi, R. Cassano, D. Dallacasa, G. Brunetti, V.   Cuciti, M. Johnston-Hollitt, N. Oozeer and O.M. Smirnov
astro-ph.CO astro-ph.GA