On the origin of very high energy gamma-rays from radio galaxies

Abstract

Radio galaxies have emerged as a new gamma-ray emitting source class on the extragalactic sky. With their jets misaligned, i.e. not directly pointing towards us, they offer a unique tool to probe some of the fundamental (and otherwise hidden) non-thermal processes in AGN. This contribution briefly summarizes the observed characteristics of the four radio galaxies detected so far at very high energies (VHE). Given its prominence, particular attention is given to the origin of the variable VHE emission in M87. We discuss some of the theoretical progress achieved for this source within recent years highlighting, amongst others, the relevance of magnetospheric particle acceleration and emission models.