Extragalactic background light and extragalactic magnetic fields

VHE γ-rays from distant blazars several hundred Mpc away are attenuated through pair production interactions on extragalactic background light (EBL). Subsequent to their generation, electron/positron pairs proceed to produce γ-rays through IC interactions leading to the development of an electromagnetic (EM) cascade. Due to the deflection of VHE cascade electrons by extragalactic magnetic fields (EGMF), the spectral shape of this arriving γ-ray emission is dependent on the strength of the EGMF. The GeV-TeV spectral shape of blazars has, thus, the potential to probe the EGMF strength along the line of sight to the object. Focusing on the specific example cases of the blazar 1ES 0229+200 and PKS 2155−304, bounds on the EGMF are obtained using both the spectral and angular observational information from the these two blazars.