Particle re-acceleration and Faraday-complex structures in the RXC
  J1314.4-2515 galaxy cluster
  Radio relics are sites of electron (re)acceleration in merging galaxy
clusters but the mechanism of acceleration and the topology of the magnetic
field in and near relics are yet to be understood. We are carrying out an
observational campaign on double relic galaxy clusters starting with RXC
J1314.4-2515. With $Jansky Very Large Array$ multi-configuration observations
in the frequency range 1-4 GHz, we perform both spectral and polarization
analyses, using the Rotation Measure synthesis technique. We use archival
$XMM-Newton$ observations to constrain the properties of the shocked region. We
discover a possible connection between the activity of a radio galaxy and the
emission of the eastern radio relic. In the northern elongated arc of the
western radio relic, we detect polarized emission with an average polarization
fraction of $31 \ \%$ at 3 GHz and we derive the Mach number of the underlying
X-ray shock. Our observations reveal low levels of fractional polarization and
Faraday-complex structures in the southern region of the relic, which point to
the presence of thermal gas and filamentary magnetic field morphology inside
the radio emitting volume. We measured largely different Rotation Measure
dispersion from the two relics. Finally, we use cosmological
magneto-hydrodynamical simulations to constrain the magnetic field, viewing
angle, and to derive the acceleration efficiency of the shock. We find that the
polarization properties of RXC J1314.4-2515 are consistent with a radio relic
observed at $70^{\circ}$ with respect to the line of sight and that efficient
re-acceleration of fossil electrons has taken place.
