AGN emission processes of NGC 4945 in the X-rays and gamma-rays

M.-L. Menzel 1 V. Beckmann 2 F. Mattana 1
2 APC - AHE
APC - UMR 7164 - AstroParticule et Cosmologie
Abstract : 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.
Document type :
Conference papers
INTEGRAL conference "The Extreme and Variable High Energy Sky", Sep 2011, Chia Laguna, Italy. pp.075


https://hal.archives-ouvertes.fr/hal-00657216
Contributor : Volker Beckmann <>
Submitted on : Friday, January 6, 2012 - 9:36:13 AM
Last modification on : Tuesday, October 28, 2014 - 6:18:04 PM

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M.-L. Menzel, V. Beckmann, F. Mattana. AGN emission processes of NGC 4945 in the X-rays and gamma-rays. INTEGRAL conference "The Extreme and Variable High Energy Sky", Sep 2011, Chia Laguna, Italy. pp.075. <hal-00657216>

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