title: New Limits on Extragalactic Magnetic Fields from Rotation Measures.
abstract: We take advantage of the wealth of rotation measures data contained in the NRAO VLA Sky Survey catalog to derive new, statistically robust, upper limits on the strength of extragalactic magnetic fields. We simulate the extragalactic magnetic field contribution to the rotation measures for a given field strength and correlation length, by assuming that the electron density follows the distribution of Lyman-α clouds. Based on the observation that rotation measures from distant radio sources do not exhibit any trend with redshift, while the extragalactic contribution instead grows with distance, we constrain fields with Jeans' length coherence length to be below 1.7 nG at the 2σ level, and fields coherent across the entire observable Universe below 0.65 nG. These limits do not depend on the particular origin of these cosmological fields.
authors.affiliation: Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetsky prospekt 13, 119992 Moscow, Russia.|Institute for Nuclear Research of the Russian Academy of Sciences, 117312 Moscow, Russia.|Pushchino Radio Astronomy Observatory, 142290 Pushchino, Russia.
authors.forename: M S
authors.initials: MS
authors.lastname: Pshirkov
authors.affiliation: Université Libre de Bruxelles, Service de Physique Théorique, CP225, 1050 Brussels, Belgium.
authors.forename: P G
authors.initials: PG
authors.lastname: Tinyakov
authors.affiliation: Université Libre de Bruxelles, Service de Physique Théorique, CP225, 1050 Brussels, Belgium.
authors.forename: F R
authors.initials: FR
authors.lastname: Urban