  Radio relics are diffuse radio sources observed in galaxy clusters, probably
produced by shock acceleration during cluster-cluster mergers. Their large
size, of the order of 1 Mpc, indicates that the emitting electrons need to be
(re)accelerated locally. The usually invoked Diffusive Shock Acceleration
models have been challenged by recent observations and theory. We report the
discovery of complex radio emission in the Galaxy cluster PLCKG287.0 +32.9,
which hosts two relics, a radio halo, and several radio filamentary emission.
Optical observations suggest that the cluster is elongated, likely along an
intergalactic filament, and displays a significant amount of substructure. The
peculiar features of this radio relic are that (i) it appears to be connected
to the lobes of a radio galaxy and (ii) the radio spectrum steepens on either
side of the radio relic. We discuss the origins of these features in the
context of particle re-acceleration.

Cosmology and Nongalactic Astrophysics;Astrophysics of Galaxies;High Energy Astrophysical Phenomena