Measuring the level of nuclear activity in Seyfert galaxies and the unification scheme

TL;DR

This study tests the Seyfert galaxy unification scheme by comparing intrinsic nuclear properties of type 1 and type 2 Seyferts, finding they are statistically similar, supporting the orientation-based unification model.

Contribution

It provides a comprehensive statistical comparison of intrinsic properties of Seyfert subtypes, confirming the unification scheme with matched samples.

Findings

Similar distributions of X-ray luminosities for both Seyfert types

Equivalent bolometric luminosities and black hole masses

Both subtypes accrete at sub-Eddington rates

Abstract

Context: The unification scheme of Seyfert galaxies hypothesizes that Seyfert type 1s and type 2s are intrinsically similar and the observed differences between the two subtypes are solely due to the differing orientations of toroidal-shaped obscuring material around the AGN. In the framework of the unification scheme, both the Seyfert subtypes are expected to show similar intrinsic nuclear properties, such as the absorption-corrected AGN X-ray luminosity, bolometric luminosity, accretion rate and the mass of the supermassive black hole. Aims: To test the predictions of the Seyfert unification scheme, we make statistical comparison of the distributions of: (i) the absorption-corrected 2.0 - 10 keV X-ray luminosities, (ii) the bolometric luminosities, (iii) the black hole masses and, (iv) the Eddington ratios, of Seyfert type 1s and type 2s. Methods: We use an optically selected Seyfert sample in which type 1s and type 2s are matched in properties that are independent to the orientation of the obscuring torus, the AGN axis and the host galaxy. Results: The distributions of the absorption-corrected 2.0 - 10 keV X-ray luminosities, the bolometric luminosities, the black masses and, the Eddington ratios are statistically similar for the two Seyfert subtypes, consistent with the orientation and obscuration based Seyfert unification scheme. The Eddington ratio distributions suggest that both the Seyfert subtypes are accreting at sub-Eddington level with wide span of Eddington ratios i.e., 10^-4 - 10^-1.