Evidence of isotropy on large distance scales from polarizations of radio sources

Abstract

We test the isotropy of radio polarization angle orientations with a robust and reliable dual-frequency polarimetric survey of active galactic nuclei (AGNs). We find that the polarization orientations are consistent with the assumption of isotropy for scales larger than or equal to ∼800 Mpc. This provides further evidence for isotropy at large distance scales and is likely to impose strong constraints on some of the physical mechanisms that may be invoked to explain past observations of alignment of radio and optical polarizations at large distance scales.