Radio Galaxies at TeV Energies: Preface

Abstract

The majority of the known extragalactic sky from TeV gamma-ray energies consists of blazars having plasma jets pointing in the direction of the line-of-sight, which results in a large Doppler boosting of their emission. Up to now, only six galaxies with a larger viewing angle have been detected in the TeV range. These objects also show fascinating properties, such as fast variability or spectral features and are called “radio galaxies”. The TeV radio galaxies provide a unique laboratory for studying key aspects of active galactic nuclei. This Special Issue of Galaxies targets these exciting objects.

Monitoring the radio galaxy M87 with HAWC

“…Radio galaxies present variability on multiple time scales, similar to Blazars [10,11]. This is the reason gamma-ray observatories started to monitor these kinds of sources.…”