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