Open AccessThe unified model and the Seyfert 2 infrared dichotomy
Author(s) -
Alexander D. M.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.04131.x
Subject(s) - physics , astrophysics , torus , galaxy , infrared , luminous infrared galaxy , line (geometry) , flux (metallurgy) , emission spectrum , astronomy , spectral line , geometry , mathematics , materials science , metallurgy
An optical spectropolarimetric study has shown that the detectability of polarized broad H α in Seyfert 2 galaxies is correlated with the IRAS f 60 f 25 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 f 60 f 25 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 H α in the cool Seyfert 2s.