TeV Active Galactic Nuclei: Multifrequency Modeling

TL;DR

This paper reviews recent TeV gamma-ray observations of active galactic nuclei, highlighting discoveries of rapid variability in blazars and the identification of radio galaxies as new VHE gamma-ray sources.

Contribution

It presents new observational results from H.E.S.S., including the active state of PKS 2155-304 and VHE gamma-ray detection from Cen A, expanding the understanding of AGN emission.

Findings

Fast variability observed in PKS 2155-304 challenges existing models.

Cen A confirmed as a VHE gamma-ray source.

Radio galaxies now recognized as VHE emitters.

Abstract

In the recent years, the new generation of Imaging Atmospheric Cerenkov Telescopes successfully detected very high energy (VHE; E>100 GeV) gamma-ray emission from a growing number of Active Galactic Nuclei (AGNs), mainly belonging to the blazar class. Among these recent results, we will mainly focus in this work on two recent discoveries made with the H.E.S.S. experiment: the tremendously active state of the blazar PKS 2155-304 observed in July 2006 and the discovery of VHE gamma-rays from the radio galaxy Cen A. On the one hand, the observation of very fast variability in PKS 2155-304 challenges the current radiative standard models for TeV blazars. On the other hand, the discovery of Cen A as a source of VHE gamma-rays firmly establishes, together with the previous detection of M 87, radio galaxies as a new class of VHE emitters.