Polarized radiative transfer modeling of warped and clumpy dusty tori
  Context: Active galactic nuclei (AGN) are anisotropic objects surrounded by
an optically thick equatorial medium whose true geometry still defy observers.
Aims: In this paper, we aim to explore the optical, scattering-induced,
polarization emerging from clumpy and warped dusty tori to check whether they
can fit with the unified model predictions. Methods: We run polarized radiative
transfer simulations in a set of warped and non warped clumpy tori to explore
the differences induced by distorted dust distributions. We then include warped
tori in a more complex model representative of an AGN to check, using
polarimetry and imaging methods, if warps can reproduce the expected
polarization dichotomy between Seyfert-1 and Seyfert-2 AGN. Results: The main
results from our simulations highlight that isolated warped structures imprint
the polarization degree and angle with distinctive signatures at Seyfert-1
orientations. Included in an AGN model, the signatures of warps are easily (but
not always) washed out by multiple scattering in a clumpy environment. Imaging
polarimetry may help to detect warped tori but we prove that warps can exist in
AGN circumnuclear regions without contradicting observations. Conclusions: Two
warped tori with a non significant difference in geometry in terms of
photometry or spectroscopy can have totally different signatures in
polarimetry. Testing the geometry of any alternative model to the usual dusty
torus using polarized radiative transfer is a necessary approach to verify or
reject a hypothesis.
