paper

X-ray spectral properties of Seyfert galaxies and the unification scheme

arXiv:1101.0252 · doi:10.1051/0004-6361/201016387

Abstract

Aims: The unification scheme of Seyfert galaxies predicts that the observed differences between type 1 and type 2 Seyfert galaxies are solely due to the differing orientations of the toroidal-shaped obscuring material around AGN. The observed X-ray spectra of Seyfert type 2s compared to type 1s are expected to be affected by higher absorbing column density due to the edge-on view of the obscuring torus. We study the 0.5 - 10 keV X-ray spectral properties of Seyfert type 1s and type 2s with the aim to test the predictions of Seyfert unification scheme in the X-ray regime. Methods: We use an optically selected Seyfert sample in which type 1s and type 2s have matched distributions in the orientation independent parameters of AGN and host galaxy. Results: The 0.5 - 10 keV XMM-Newton pn X-ray spectra of Seyfert galaxies are in general best fitted with a model consists of an absorbed power-law, a narrow Gaussian fitted to the Fe Kα emission line and an often seen soft excess component characterized by either a thermal plasma model with temperature kT \sim 0.1 - 1.0 keV and/or a steep power-law. The 2.0 - 10 keV hard X-ray continuum emission in several Seyfert type 2s is reflection dominated and suggests the Compton-thick obscuration. Results on the statistical comparison of the distributions of the observed X-ray luminosities in the soft (0.5 - 2.0 keV) and hard (2.0 - 10.0 keV) bands, the X-ray absorbing column densities, the equivalent widths of Fe Kα line and the flux ratios of hard X-ray to [OIII] λ5007Å for the two Seyfert subtypes are consistent with the obscuration and orientation based unification scheme.

arXiv comment15 pages, 3 figures, 6 tables, accepted for publication in A&A

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