Signatures from a merging galaxy cluster and its AGN population: LOFAR
  observations of Abell 1682
  We present LOFAR data from 110--180~MHz of the merging galaxy cluster Abell
1682, alongside archival optical, radio and X-ray data. Our 6 arc-second
resolution images at low frequencies reveal new structures associated with
numerous radio galaxies in the cluster. At 20 arc-second resolution we see
diffuse emission throughout the cluster over hundreds of kpc, indicating
particle acceleration mechanisms are in play as a result of the cluster merger
event and powerful active galactic nuclei. We show that a significant part of
the cluster emission is from an old radio galaxy with very steep spectrum
emission (having a spectral index of $\alpha < -2.5$). Furthermore we identify
a new region of diffuse steep spectrum emission ($\alpha < -1.1$) as a
candidate for a radio halo which is co-spatial with the centre of the cluster
merger. We suggest its origin as a population of old and mildly relativistic
electrons left over from radio galaxies throughout the cluster which have been
re-accelerated to higher energies by shocks and turbulence induced by the
cluster merger event. We also note the discovery of six new giant radio
galaxies in the vicinity of Abell 1682.
