UV and optical polarization modeling of thermal active galactic nuclei :
  impact of the narrow line region
  In this research note, we start exploring the influence of the narrow line
region (NLR) on the optical/UV continuum polarization of active galactic nuclei
(AGN). We have upgraded our previous 3-component model of a thermal Seyfert
nucleus that was composed of an equatorial, optically thin electron disc, a
circumnuclear dusty torus, and a pair of collimated, optically thin electron
winds (Marin et al.2012b). We have added a dusty extension with low optical
depth to the outflows to account for continuum scattering and absorption inside
the NLR. A spectropolarimetric comparison between our AGN models with and
without NLR reprocessing is carried out. It turns out that the NLR can alter
and even suppress the observed polarization dichotomy between type-1 and type-2
AGN. For type-2 AGN, it also significantly decreases the expected percentage of
polarization and alters its spectral shape. While the NLR makes it more
difficult to reproduce the observed polarization in type-1 objects, it helps to
explain spectropolarimetry observations of type-2 objects. Further studies
including clumpy media need to be carried out.
