MeerKAT Reveals Evidence of a Radio Megahalo at GHz Frequency

Abstract

Radio megahalos are recently discovered large-scale diffuse synchrotron sources identified through LOFAR observations. We present MeerKAT L-band observations of the massive galaxy cluster RXC~J0528.9$-$3927, that reveals faint emission surrounding its central radio halo. At 1.28 GHz, the known $\sim1.14$ Mpc halo is embedded within previously unreported low-surface-brightness emission extending to $\sim2$ Mpc. The surface-brightness profile of the emission shows a distinct flattening beyond $\sim0.55R_{500}$, suggesting that the outer emission forms an additional component. These properties make the cluster a candidate megahalo system and potentially the first detected at GHz frequencies, although deeper multi-frequency observations are required for confirmation.