Radio observations of the merging galaxy cluster system Abell 3391-Abell
  3395
  The pre-merging system of galaxy clusters Abell 3391-Abell 3395 located at a
mean redshift of 0.053 has been observed at 1 GHz in an ASKAP/EMU Early Science
observation as well as in X-rays with eROSITA. The projected separation of the
X-ray peaks of the two clusters is $\sim$50$'$ or $\sim$ 3.1 Mpc. Here we
present an inventory of interesting radio sources in this field around this
cluster merger. While the eROSITA observations provide clear indications of a
bridge of thermal gas between the clusters, neither ASKAP nor MWA observations
show any diffuse radio emission coinciding with the X-ray bridge. We derive an
upper limit on the radio emissivity in the bridge region of $\langle J
\rangle_{1\,{\rm GHz}}< 1.2 \times 10^{-44} {\rm W}\, {\rm Hz}^{-1} {\rm
m}^{-3}$. A non-detection of diffuse radio emission in the X-ray bridge between
these two clusters has implications for particle-acceleration mechanisms in
cosmological large-scale structure. We also report extended or otherwise
noteworthy radio sources in the 30 deg$^2$ field around Abell 3391-Abell 3395.
We identified 20 Giant Radio Galaxies, plus 7 candidates, with linear projected
sizes greater than 1 Mpc. The sky density of field radio galaxies with largest
linear sizes of $>0.7$ Mpc is $\approx 1.7$ deg$^{-2}$, three times higher than
previously reported. We find no evidence for a cosmological evolution of the
population of Giant Radio Galaxies. Moreover, we find seven candidates for
cluster radio relics and radio halos.
