Abstract :
Radio relics are Mpc-size synchrotron sources observed in the
outskirts of some merging galaxy clusters. Their radio emission fills large
volumes of the intracluster medium (ICM), unveiling the presence of a
non-thermal component mixed with the thermal gas, i.e. relativistic
electrons and magnetic fields. The origin of radio relics is recognized to
be connected to shock waves injected in the ICM during cluster mergers.
Yet, the details of particle acceleration processes leading to their
emission are unclear. Furthermore, magnetic fields in radio relics, and in
galaxy clusters in general, are difficult to measure and still poorly
known. However, being highly polarized, radio relics offer a peculiar view
of their magnetic fields by studying their polarization and
Faraday rotation properties. In this talk, I will review recent advances in
the knowledge of radio relics' origin, focusing on their polarized emission.
