A giant radio bridge connecting two clusters in Abell 1758
  Collisions between galaxy clusters dissipate enormous amounts of energy in
the intra-cluster medium (ICM) through turbulence and shocks. In the process,
Mpc-scale diffuse synchrotron emission in form of radio halos and relics can
form. However, little is known about the very early phase of the collision. We
used deep radio observations from 53 MHz to 1.5 GHz to study the pre-merging
galaxy clusters A1758N and A1758S that are $\sim2$ Mpc apart. We confirm the
presence of a giant bridge of radio emission connecting the two systems that
was reported only tentatively in our earlier work. This is the second
large-scale radio bridge observed to date in a cluster pair. The bridge is
clearly visible in the LOFAR image at 144 MHz and tentatively detected at 53
MHz. Its mean radio emissivity is more than one order of magnitude lower than
that of the radio halos in A1758N and A1758S. Interestingly, the radio and
X-ray emissions of the bridge are correlated. Our results indicate that
non-thermal phenomena in the ICM can be generated also in the region of
compressed gas in-between infalling systems.
