| Domaine : |
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| Titre : |
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AGN emission processes of NGC 4945 in the X-rays and gamma-rays |
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| Auteur(s) : |
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M.-L. Menzel1, V. Beckmann1, F. Mattana1 |
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| Laboratoire : |
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| équipe(s) de recherche : |
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APC - AHE |
| Résumé : |
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NGC 4945 has an outstanding role among the Seyfert 2 active galatic nuclei (AGN) because it is one of the few non-blazars which have been detected in the gamma-rays. Here, we analyse the high energy spectrum using Suzaku, INTEGRAL and Fermi data. We reconstruct the spectral energy distribution in the soft X-ray to gamma-ray domain in order to provide a better understanding of the processes in the AGN. We present two models to fit the high-energy data. The first model assumes that the gamma-ray emission originates from one single non-thermal component, e.g. a shock-induced pion decay caused by the starburst processes in the host galaxy, or by interaction with cosmic rays. The second model describes the high-energy spectrum by two independent components: a thermal inverse Compton process of photons in the non-beamed AGN and a non-thermal emission of the gamma-rays. These components are represented by an absorbed cut-off power law for the thermal component in the X-ray energy range and a simple power law for the non-thermal component in the gamma-rays. For the thermal process, we obtain a photon index of Gamma=1.6, a cut-off energy of Ec ~ 150 keV and a hydrogen column density of NH = 6e24 1/cm**2. The non-thermal process has a photon index of Gamma=2.0 and a flux of F(0.1-100 GeV) = 1.4e-11 erg/cm**2/sec. The spectral energy distribution gives a total unabsorbed flux of F(2 keV - 100 GeV) = 5e-10 erg/cm**2/sec and a luminosity of L(2 keV - 100 GeV) = 9e41 erg/sec at a distance of 3.7 Mpc. It appears more reasonable that the gamma-ray emission is independent from the AGN and could be caused e.g. by shock processes in the starburst regions of the host galaxy. |
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Langue du texte
intégral : |
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Anglais |
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| Titre de l'ouvrage : |
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The Extreme and Variable High Energy Sky |
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| Audience : |
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internationale |
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| Type de publication : |
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Communications avec actes |
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| Date de publication : |
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01/2012 |
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| Page, identifiant, ... : |
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075 |
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| Titre de la conférence : |
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INTEGRAL conference "The Extreme and Variable High Energy Sky" |
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| Date de la conférence : |
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19/09/2011 |
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| Date de la conférence (fin) : |
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23/09/2011 |
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| Ville : |
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Chia Laguna |
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| Pays : |
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Italie |
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| Mots Clés : |
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Astrophysics - High Energy Astrophysical Phenomena |
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| Commentaire : |
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6 pages, 2 figures, proceedings of the INTEGRAL conference "The Extreme and Variable High Energy Sky", held on September 19-23, 2011 in Chia Laguna (Italy); accepted for publication in Proceedings of Science, SISSA, PoS(Extremesky 2011)075 |
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