Abstract
We study 12 Seyfert 1 galaxies with a high level of optical polarization. Optical light emerging from the innermost regions is predominantly scattered in a polar region above the central engine directly in our line of sight. These sources show characteristics of Seyfert 2 galaxies, e.g. polarized broad lines. The polarization signatures suggest a viewing angle of 45°, classifying them as intermediate Seyfert 1/2 types. The unified model predicts this line of sight to pass through the outer layer of the torus resulting in significant soft X-ray variability due to a strongly varying column density. The aim is to find evidence for this geometrical assumption in the spectral variability of all available historical observations of these sources by <em>XMM-Newton</em> and <em>Swift</em>.
Highlights
According to the unified model of Active Galactic Nuclei/AGN [1] Seyfert 1 and Seyfert 2 galaxies are the same type of galaxies, but seen under different inclination angles (Fig. 1)
Optical light emerging from the innermost regions is predominantly scattered in a polar region above the central engine directly in our line of sight
The unified model predicts this line of sight to pass through the outer layer of the torus resulting in significant soft X-ray variability due to a strongly varying column density
Summary
According to the unified model of Active Galactic Nuclei/AGN [1] Seyfert 1 and Seyfert 2 galaxies are the same type of galaxies, but seen under different inclination angles (Fig. 1). The line of sight towards these galaxies passes through the outer layers of the torus, where significant absorption is still expected and suppresses polarized light from the equatorial scattering region, but not the polar-scattered light. We assume these outer layers to be a non-homogeneous gas and dust medium which might be stripped off by nuclear radiation resulting in a highly variable column density towards the observer. Theory [4, 9] predicts a relatively cold, dense phase in equilibrium with partially ionized gas forming the broad line region (BLR) These embedded BLR clouds are commonly believed to be gravitationally bound to the center of mass. In contrast to the dusty outer layer of the torus, we assume ionized absorbers to fully cover the line-of-sight [3]
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