Study of diffuse emission in cluster MACSJ0417.5-1154 from 76 MHz to 18 GHz

Abstract

We present new radio observations of the massive and X-ray luminous galaxy cluster MACS J0417.5–1154, at 1.387 GHz and 18 GHz, from the Giant Metrewave Radio Telescope (GMRT) and the Australia Telescope Compact Array (ATCA) respectively. We estimate diffuse emission in the central region of the cluster at 1.387 GHz and 18 GHz. We combine these data with previously published results and present the spectrum of diffuse emission from 76 MHz to 18 GHz. This is possibly a unique study of the radio halo emission in galaxy cluster over this wide range of frequencies. Such studies lay the prospects of future studies with radio telescopes with wide-range of frequencies like the Square Kilometre Array (SKA). Our 1.387 GHz data, with 2 ″ angular resolution, provides a better estimate of point source emission than previous L-band observations, which is crucial, given the claim of sharp steepening of the radio halo spectrum at 0.61 GHz reported earlier. We find that the spectrum of the radio halo has a spectral index fit up to 18 GHz, and yields a spectral index between 76 MHz and 18 GHz that fits the available data better than earlier L-band observations. We discuss possible reasons for the peculiar spectral characteristics of the diffuse emission. © 2019, Indian Academy of Sciences.