The Unified model and the Seyfert 2 infrared dichotomy

Abstract

An optical spectropolarimetric study has shown that the detectability of polarised broad H-alpha in Seyfert 2 galaxies is correlated to the IRAS f60/f25 flux ratio where only those Seyfert 2s with "warm" IRAS colours show polarised 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 suggest 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 polarised broad H-alpha in the cool Seyfert 2s.