Polarization of radio relics in galaxy clusters

Abstract

ABSTRACT Radio emission in the form of giant radio relics is observed at the periphery of galaxy clusters. This non-thermal emission is an important tracer for cosmic ray electrons and intracluster magnetic fields. One striking observational feature of these objects is their high degree of polarization, which provides information on the magnetic fields at the relics’ positions. In this contribution, we test if state-of-the-art high resolution cosmological simulations are able to reproduce the polarization features of radio relics. Therefore, we present a new analysis of high-resolution cosmological simulations to study the polarization properties of radio relics in detail. In order to compare our results with current and future radio observations, we create mock radio observations of the diffuse polarized emission from a massive galaxy cluster using six different projections, for different observing frequencies and for different telescopes. Our simulations suggest that, due to the effect of Faraday rotation, it is extremely difficult to relate the morphology of the polarized emission for observing frequencies below 1.4 GHz to the real magnetic field structure in relics. We can reproduce the observed degree of polarization and also several small-scale structures observed in real radio relics, but further work would be needed to reproduce some large-scale spectacular features as observed in real radio relics, such as the ‘Sausage’ and ‘Toothbrush’ relics.