The large-scale diffuse radio emission in A781
  A781 belongs to a complex system characterized by extended X-ray emissions
that may form part of line of clusters of galaxies along a filament. The aim of
this work is to investigate the possible presence of extended, diffuse
synchrotron radio emission connected to the intra-cluster medium of A781. We
studied the radio continuum emission and the spectral index properties in
proximity of the A781 by analyzing archival Very Large Array observations at
1400 and 325 MHz. The main cluster of the system is permeated by diffuse
low-surface brightness radio emission which is classified, being located close
to the center, as a radio halo. The diffuse emission presents the typical
extension and radio power of the other halos known in the literature.
Interestingly, the radio halo appears to be linked to a peripheral patch
previously found in the literature. The spectrum of this peripheral emission
shows a radial steepening which may confirm that this source is indeed a
cluster relic.
