Intergalactic Magnetic Fields and Extreme TeV Blazars
Very High Energy (VHE) gamma-rays (E > 100 GeV) emitted from distant Active Galactic Nuclei interact with the diffuse far-IR to UV extragalactic background light (EBL) in intergalactic space, producing electron positron pairs. These pairs are deflected by the intergalactic magnetic field (IGMF), and in turn, inverse Compton (IC) scatter CMB and EBL photons up to GeV-TeV energies, as delayed secondary emission. For hard spectrum "Extreme" sources, the secondary IC emission thus produced modifies the observed spectrum of the source, and is potentially detectable by IACTs and the Fermi-LAT instrument. We review recent constraints on IGMF which were reported in the literature and derived for 3 TeV-detected blazars-1ES 0229+200, 1ES 1218+304, and RGB J0710+591. Through detailed Monte Carlo simulations, incorporating all major effects of QED and cosmological expansion, we research effects of major uncertainties such as the past history of emission, spectral properties of the source, undersampled IACT coverage, source vs. observer geometry, and AGN jet Doppler factor. The implications of these effects on the recently reported lower limits of the IGMF will be thoroughly examined.
