Compton-induced HE–VHE γ-rays from pair cascade emissions in the SEDs of radio galaxies: NGC 1275

Abstract

In the scheme of active galactic nuclei (AGNs), the blazar subclass is particularly bright in -rays. This is because of their emissions being beamed into our line of sight, as opposed to their misaligned parent population, radio galaxies. This work presents results of a Monte Carlo (mc) code that propagates jet-collimated -rays through the magnetized AGN environment, leading to secondary cascade emissions from relativistic electron-positron pairs. The resulting multiwavelength emissions are used to fit the broad-band spectral energy distribution (SED) of the radio galaxy NGC 1275. Using known physical parameters of NGC 1275 from the literature, we find that cascade emissions from stochastic processes have the potential to reproduce the broad-band SEDs of radio galaxies. We also find that the interplay between accretion disc and broad-line region (BLR) photons may provide insights into the production region(s) of -rays in AGNs. While dense accretion disc and BLR radiation fields are vital to the development of cascades, excessive densities lead to the suppression of cascade synchrotron emission and attenuation of TeV -rays. Furthermore, the magnetic field is important in shaping the cascade -ray spectrum.