The unified model and the Seyfert 2 infrared dichotomy

Abstract

An optical spectropolarimetric study has shown that the detectability of polarized broad Hα in Seyfert 2 galaxies is correlated with the IRAS f60/f25 flux ratio where only those Seyfert 2s with 'warm' IRAS colours show polarized broad-line emission. It was suggested that those Seyfert 2s with 'cool' IRAS colours have highly inclined tori which obscure the broad-line scattering screen. I present here hard X-ray observations inconsistent with this picture, showing that the derived column densities of warm and cool Seyfert 2 galaxies are statistically the same. I classify the Bright Galaxy Sample to produce a non-Seyfert comparison. The analysis of the properties of these galaxies with the Seyfert 2s suggests that the IRAS f60/f25 flux ratio is consistent with implying the relative strength of galactic to Seyfert emission. I show that this new picture can account for the absence of polarized broad Hα in the cool Seyfert 2s.