KAT-7 detection of radio halo emission in the Triangulum Australis galaxy cluster

Abstract

We report the presence of high significance diffuse radio emission from the Triangulum Australis cluster using observations made with the KAT-7 telescope and propose that this emission is a giant radio halo. We compare the radio power from this proposed halo with X-ray and SZ measurements and demonstrate that it is consistent with the established scaling relations for cluster haloes. By combining the X-ray and SZ data we calculate the ratio of non-thermal to thermal electron pressure within Triangulum Australis to be $X=0.658\pm0.054$. We use this ratio to constrain the maximum magnetic field strength within the halo region to be $B_{\rm max, halo} = 33.08\,\mu$G and compare this with the minimum field strength from equipartition of $B_{\rm min, halo} = 0.77(1+k)^{2/7}\,\mu$G to place limits on the range of allowed magnetic field strength within this cluster. We compare these values to those for more well-studied systems and discuss these results in the context of equipartition of non-thermal energy densities within clusters of galaxies.