Lower limit on the strength and filling factor of extragalactic magnetic fieldsстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:High energy photons from blazars can initiate electromagnetic pair cascades interacting with the
extragalactic photon background. The charged component of such cascades is deflected and delayed
by extragalactic magnetic fields (EGMF), reducing thereby the observed point-like flux and leading
potentially to multi degree images in the GeV energy range. We calculate the fluence of 1ES 0229+200
as seen by Fermi-LAT for different EGMF profiles using a Monte Carlo simulation for the cascade
development. The non-observation of 1ES 0229+200 by Fermi-LAT suggests that the EGMF fills
at least 60% of space with fields stronger than O(10−16 − 10−15) G for life times of TeV activity
of O(102 − 104 ) yr. Thus the (non-) observation of GeV extensions around TeV blazars probes the
EGMF in voids and puts strong constraints on the origin of EGMFs: Either EGMFs were generated
in a space filling manner (e.g. primordially) or EGMFs produced locally (e.g. by galaxies) have to be
efficiently transported to fill a significant volume fraction, as e.g. by galactic outflows.