Evidence for strong extragalactic magnetic fields from Fermi observations of TeV blazars

2010/06/17 by Andrii Neronov, Ievgen Vovk · 7 citations
Physics and Astronomy · #astro-ph.HE

paper · pdf · doi:10.1126/science.1184192

published as Science 328:73-75,2010 · 14 pages, 3 figures

arxiv created 2010/06/17 · arxiv updated 2014/11/21

Abstract

Magnetic fields in galaxies are produced via the amplification of seed magnetic fields of unknown nature. The seed fields, which might exist in their initial form in the intergalactic medium, were never detected. We report a lower bound B≥ 3× 10^-16~gauss on the strength of intergalactic magnetic fields, which stems from the nonobservation of GeV gamma-ray emission from electromagnetic cascade initiated by tera-electron volt gamma-ray in intergalactic medium. The bound improves as λ_B^-1/2 if magnetic field correlation length, λ_B, is much smaller than a megaparsec. This lower bound constrains models for the origin of cosmic magnetic fields.

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