The H.E.S.S. extragalactic sky

TL;DR

The H.E.S.S. telescope array has significantly advanced the understanding of extragalactic gamma-ray sources, discovering new sources, observing rapid variability, and constraining the extragalactic background light through extensive observations and multi-wavelength studies.

Contribution

This paper presents new results from H.E.S.S. observations of extragalactic sources, highlighting discoveries and implications for AGN physics and gamma-ray emission mechanisms.

Findings

Discovery of new extragalactic VHE gamma-ray sources.

Observation of rapid variability in AGN emissions.

Constraints on the extragalactic background light density.

Abstract

The H.E.S.S. Cherenkov telescope array, located on the southern hemisphere in Namibia, studies very high energy (VHE; E>100 GeV) gamma-ray emission from astrophysical objects. During its successful operations since 2002 more than 80 galactic and extra-galactic gamma-ray sources have been discovered. H.E.S.S. devotes over 400 hours of observation time per year to the observation of extra-galactic sources resulting in the discovery of several new sources, mostly AGNs, and in exciting physics results e.g. the discovery of very rapid variability during extreme flux outbursts of PKS 2155-304, stringent limits on the density of the extragalactic background light (EBL) in the near-infrared derived from the energy spectra of distant sources, or the discovery of short-term variability in the VHE emission from the radio galaxy M 87. With the recent launch of the Fermi satellite in 2008 new insights into the physics of AGNs at GeV energies emerged, leading to the discovery of several new extragalactic VHE sources. Multi-wavelength observations prove to be a powerful tool to investigate the production mechanism for VHE emission in AGNs. Here, new results from H.E.S.S. observations of extragalactic sources will be presented and their implications for the physics of these sources will be discussed.