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 Lymanα 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 2 σ 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.
 Publication:

Physical Review Letters
 Pub Date:
 May 2016
 DOI:
 10.1103/PhysRevLett.116.191302
 arXiv:
 arXiv:1504.06546
 Bibcode:
 2016PhRvL.116s1302P
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 5 pages, 3 figures  v2 to match PRL version