The first Murchison Widefield Array low frequency radio observations of cluster scale non-thermal emission: the case of Abell 3667

TL;DR

This study presents the first low-frequency radio observations of galaxy cluster Abell 3667 using the Murchison Widefield Array, detecting radio relics and potential halo features, and analyzing their spectral properties to understand non-thermal emission.

Contribution

It provides new low-frequency observations of Abell 3667, revealing detailed spectral properties of radio relics and potential diffuse emission features.

Findings

Detected NW and SE radio relics with specific flux densities

Observed spectral index variation indicating electron aging

Possible detection of radio halo and bridge features

Abstract

We present the first Murchison Widefield Array observations of the well-known cluster of galaxies Abell 3667 (A3667) between 105 and 241 MHz. A3667 is one of the best known examples of a galaxy cluster hosting a double radio relic and has been reported to contain a faint radio halo and bridge. The origins of radio halos, relics and bridges is still unclear, however galaxy cluster mergers seems to be an important factor. We clearly detect the North-West (NW) and South-East (SE) radio relics in A3667 and find an integrated flux density at 149 MHz of 28.1 +/- 1.7 and 2.4 +/- 0.1 Jy, respectively, with an average spectral index, between 120 and 1400 MHz, of -0.9 +/- 0.1 for both relics. We find evidence of a spatial variation in the spectral index across the NW relic steepening towards the centre of the cluster, which indicates an ageing electron population. These properties are consistent with higher frequency observations. We detect emission that could be associated with a radio halo and bridge. How- ever, due to the presence of poorly sampled large-scale Galactic emission and blended point sources we are unable to verify the exact nature of these features.