Obscuration in the Host Galaxies of Soft X‐Ray–selected Seyfert Nuclei

Abstract

We define a new sample of 96 low-redshift (z < 0.1), soft X-ray-selected Seyfert galaxies from the catalog of the Einstein Slew Survey. We probe the geometry and column depth of obscuring material in the host-galaxy disks using galactic axial ratios determined mainly from the Digitized Sky Survey. The distribution of host-galaxy axial ratios clearly shows a bias against edge-on spirals, which confirms the existence of a geometrically thick layer of obscuring material in the host-galaxy planes. Soft X-ray selection recovers some of the edge-on objects missed in UV and visible surveys but still results in 30% incompleteness for type 1 nuclei. We speculate that thick rings of obscuring material such as the ones we infer for these Seyfert galaxies might be commonly present in early-type spirals, sitting at the inner Lindblad resonances of the nonaxisymmetric potentials of the host galaxies.