A study of halo and relic radio emission in merging clusters using the
  Murchison Widefield Array
  We have studied radio haloes and relics in nine merging galaxy clusters using
the Murchison Widefield Array (MWA). The images used for this study were
obtained from the GaLactic and Extragalactic All-sky MWA (GLEAM) Survey which
was carried out at 5 frequencies, viz. 88, 118, 154, 188 and 215 MHz. We detect
diffuse radio emission in 8 of these clusters. We have estimated the spectra of
haloes and relics in these clusters over the frequency range 80-1400 MHz; the
first such attempt to estimate their spectra at low frequencies. The spectra
follow a power law with a mean value of $\alpha = -1.13\pm0.21$ for haloes and
$\alpha = -1.2\pm0.19$ for relics where, $S \propto \nu^{\alpha}$. We
reclassify two of the cluster sources as radio galaxies. The low frequency
spectra are thus an independent means of confirming the nature of cluster
sources. Five of the nine clusters host radio haloes. For the remaining four
clusters, we place upper limits on the radio powers of possible haloes in them.
These upper limits are a factor of 2-20 below those expected from the $L_{\rm
X}-P_{\rm 1.4}$ relation. These limits are the lowest ever obtained and the
implications of these limits to the hadronic model of halo emission are
discussed.
