An analysis of the halo and relic radio emission from Abell 3376 from
  Murchison Widefield Array observations
  We have carried out multiwavelength observations of the near-by ($z=0.046$)
rich, merging galaxy cluster Abell 3376 with the Murchison Widefield Array
(MWA). As a part of the GaLactic and Extragalactic All-sky MWA survey (GLEAM),
this cluster was observed at 88, 118, 154, 188 and 215 MHz. The known radio
relics, towards the eastern and western peripheries of the cluster, were
detected at all the frequencies. The relics, with a linear extent of $\sim$ 1
Mpc each, are separated by $\sim$ 2 Mpc. Combining the current observations
with those in the literature, we have obtained the spectra of these relics over
the frequency range 80 -- 1400 MHz. The spectra follow power laws, with
$\alpha$ = $-1.17\pm0.06$ and $-1.37\pm0.08$ for the west and east relics,
respectively ($S \propto \nu^{\alpha}$). Assuming the break frequency to be
near the lower end of the spectrum we estimate the age of the relics to be
$\sim$ 0.4 Gyr. No diffuse radio emission from the central regions of the
cluster (halo) was detected. The upper limit on the radio power of any possible
halo that might be present in the cluster is a factor of 35 lower than that
expected from the radio power and X-ray luminosity correlation for cluster
halos. From this we conclude that the cluster halo is very extended ($>$ 500
kpc) and/or most of the radio emission from the halo has decayed. The current
limit on the halo radio power is a factor of ten lower than the existing upper
limits with possible implications for models of halo formation.
