Friday, July 19, 2013

1307.4823 (L. Stawarz et al.)

Active Galaxies Studied with the H.E.S.S. Observatory    [PDF]

L. Stawarz, for the H. E. S. S. Collaboration
X-ray selected BL Lac objects dominate the population of extragalactic sources detected in the very high energy (VHE; photon energies >100GeV) gamma-ray regime with ground-based Cherenkov Telescopes. These are not the only extragalactic VHE emitters, however, since also other types of active galactic nuclei (AGN) have recently been established as VHE sources as well. They include radio galaxies, optically-selected BL Lacs, and Flat-Spectrum Radio Quasars. Here we review the current status of the ongoing AGN studies with the H.E.S.S. instrument, concentrating on the following main three topics: (i) constraints on the structure of the blazar emitting zone, and on the energy dissipation processes involved in the production of the high-energy emission in AGN, enabled by detailed timing and spectral analysis of the H.E.S.S. data; (ii) constraints on the extragalactic background light (EBL) using H.E.S.S. observations of blazars, and (iii) the phenomenological picture of the gamma-ray loud AGN population emerging from combined VHE and multi-wavelength observations of different classes of active galaxies.
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