Constraints on the extragalactic magnetic fields from the NVSS Faraday rotation measures

We use rotation measures data from the NVSS catalogue to derive new, statistically robust, upper limits on the strength of extragalactic magnetic fields. The extragalactic contribution to the rotation measures for a given field strength and correlation length grows with the distance. Based on the observation that low-luminosity distant radio sources do not exhibit any trend with their redshift, we then constrain extragalactic fields with Mpc coherence length to be below approximately 1.5 nG; a field coherent across the entire observable Universe instead is bounded to be below 0.6 nG. These limits do not depend on the particular origin of these cosmological fields.SCOPUS: cp.p