Mini-radio lobes in AGN core illumination and their hadronic gamma-ray afterlight

Abstract

Recent radio observations reveal the existence of mini-radio lobes in active galaxies with scales of ~10 pc. The lobes are expected to be filled with shock-accelerated electrons and protons. In this work, we examine the photon spectra from the mini-lobes, properly taking the hadronic processes into account. We find that the resultant broad-band spectra contain the two distinct hadronic bumps in γ-ray bands, i.e. the proton synchrotron bump at ~1MeV and the synchrotron bump at ~1 GeV due to the secondary electrons/positrons produced via photo-pion cascade. In particular, when the duration of particle injection is shorter than the lobe age, radio-dark γ -ray lobes are predicted. The existence of the γ -ray lobes could be testable with the future TeV-γ Cherenkov Telescope Array. © 2010 The Authors. Monthly Notices of the Royal Astronomical Society.