Sensitivity ofγ-ray telescopes for detection of magnetic fields in the intergalactic medium

Abstract

We explore potential of current and next-generation $\ensuremath{\gamma}$-ray telescopes for the detection of weak magnetic fields in the intergalactic medium. We demonstrate that using two complementary techniques, observation of extended emission around point sources and observation of time delays in $\ensuremath{\gamma}$-ray flares, one would be able to probe most of the cosmologically and astrophysically interesting part of the ``magnetic field strength'' vs ``correlation length'' parameter space. This implies that $\ensuremath{\gamma}$-ray observations with Fermi and ground-based Cherenkov telescopes will allow to (a) strongly constrain theories of the origin of magnetic fields in galaxies and galaxy clusters and (b) discover, constrain or rule out the existence of weak primordial magnetic field generated at different stages of evolution of the Early Universe.