Radio Galaxies at VHE Energies

Abstract

Radio Galaxies have by now emerged as a new γ-ray emitting source class on the extragalactic sky. Given their remarkable observed characteristics, such as unusual gamma-ray spectra or ultrafast VHE variability, they represent unique examples to probe the nature and physics of active galactic nuclei (AGN) in general. This review provides a compact summary of their observed characteristics at very high γ-ray energies (VHE; greater than 100 GeV) along with a discussion of their possible physics implications. A particular focus is given to a concise overview of fundamental concepts concerning the origin of variable VHE emission, including recent developments in black hole gap physics.