A method of measurement of extragalactic magnetic fields by TeV gamma ray telescopes
A. Neronov, D. V .Semikoz+
Integral Science Data Center, Chemin d'Écogia 16, 1290 Versoix, Switzerland
and Geneva Observatory, CH-1290 Sauverny, Switzerland
+APC, Collège de France, 75005 Paris, France
and
Institute for Nuclear Research RAS, 117312 Moscow, Russia
PACS: 95.85.Pw, 98.62.En
Abstract
We propose a method of measurement of extragalactic magnetic
fields in observations of TeV γ rays from distant sources. Multi-TeV
γ rays from these sources interact with the infrared photon
background producing secondary electrons and positrons, which can be just
slightly deflected by extragalactic magnetic fields before they emit
secondary γ rays via inverse Compton scattering of cosmic microwave
background photons. Secondary γ rays emitted toward an observer on
the Earth can be detected as extended emission around initially point source.
Energy dependent angular profile of extended emission is related to the
strength of extragalactic magnetic field along the line of sight. Small
magnetic fields
G in the voids of the large scale structure
can be measured in this way.