Predicting the X-ray polarization of type-2 Seyfert galaxies
  Infrared, optical and ultraviolet spectropolarimetric observations have
proven to be ideal tools for the study of the hidden nuclei of type-2 active
galactic nuclei (AGN) and for constraining the composition and morphology of
the sub-parsec scale emission components. In this paper, we extend the analysis
to the polarization of the X-rays from type-2 AGN. Combining two radiative
transfer codes, we performed the first simulations of photons originating in
the gravity dominated vicinity of the black hole and scattering in structures
all the way out to the parsec-scale torus and polar winds. We demonstrate that,
when strong gravity effects are accounted for, the X-ray polarimetric signal of
Seyfert-2s carries as much information about the central AGN components as
spectropolarimetric observations of Seyfert-1s. The spectropolarimetric
measurements can constrain the spin of the central supermassive black hole even
in edge-on AGN, the hydrogen column density along the observer's line-of-sight,
and the composition of the polar outflows. However, the polarization state of
the continuum source is washed out by multiple scattering, and should not be
measurable unless the initial polarization is exceptionally strong. Finally, we
estimate that modern X-ray polarimeters, either based on the photo-electric
effect or on Compton scattering, will require long observational times on the
order of a couple of mega-seconds to be able to properly measure the
polarization of type-2 AGN.
