First look Murchison Widefield Array observations of Abell 3667

The Murchison Widefield Array (MWA) is a new low frequency interferometric radio telescope, operating in the remote Murchison Radio Observatory in Western Australia. In this paper we present the first MWA observations of the well known radio relics in Abell 3667 (A3667) between 120 and 226 MHz. We clearly detect the radio relics in A3667 and present flux estimates and spectral indices for these features. The average spectral index of the north-west (NW) and south-east (SE) relics is −0.9 ± 0.1 between 120 and 1400 MHz. We are able to resolve spatial variation in the spectral index of the NW relic from −1.7 to −0.4, which is consistent with results found at higher frequencies.

1. Introduction

Observations of galaxy clusters in the radio regime have revealed low surface brightness and large-scale non-thermal emission up to Mpc-scales associated with some galaxy clusters. These radio sources are known as radio halos and relics and share some observational properties: they have steep synchrotron spectra and are characterised by low surface brightness emission ( Jy arcsec=). Radio halos are unpolarised and located towards the centre of the host galaxy cluster, whilst relics are highly polarised and reside on the periphery of the galaxy cluster.