@article{01J9KM6PD7HBQA2XDC8FNM8JRQ,
  abstract     = {{Context : 
Cold gas and dust reprocess the central X-ray emission of active galactic nuclei (AGN), producing characteristic spectro-polarimetric features in the X-ray band. The recent launch of IXPE allows for observations of this X-ray polarisation signal, which encodes unique information on the parsec-scale circumnuclear medium of obscured AGN. However, the models for interpreting these polarimetric data are under-explored and do not reach the same level of sophistication as the corresponding spectral models. 

Aims : 
We aim at closing the gap between the spectral and spectro-polarimetric modelling of AGN circumnuclear media in the X-ray band by providing the tools for simulating X-ray polarisation in complex geometries of cold gas alongside X-ray spectra. 

Methods : 
We lay out the framework for X-ray polarisation in 3D radiative transfer simulations and provide an implementation to the 3D radiative transfer code SKIRT, focussing on (de)polarisation due to scattering and fluorescent re-emission. As an application, we explored the spectro-polarimetric properties of a 2D toroidal reprocessor of cold gas, modelling the circumnuclear medium of AGN. 

Results : 
For the 2D torus model, we find a complex behaviour of the polarisation angle with photon energy, which we interpret as a balance between the reprocessed photon flux originating from different sky regions, with a direct link to the torus geometry. We calculated a large grid of AGN torus models and demonstrated how spatially resolved X-ray polarisation maps could form a useful tool for interpreting the geometrical information that is encoded in IXPE observations. With this work, we release high-resolution AGN torus templates that simultaneously describe X-ray spectra and spectro-polarimetry for observational data fitting with XSPEC. 

Conclusions : The SKIRT code can now model X-ray polarisation simultaneously with X-ray spectra and provide synthetic spectro-polarimetric observations for complex 3D circumnuclear media, with all features of the established SKIRT framework available.}},
  articleno    = {{A297}},
  author       = {{Vander Meulen, Bert and Camps, Peter and Savić, Ðorđe and Baes, Maarten and Matt, Giorgio and Stalevski, Marko}},
  issn         = {{0004-6361}},
  journal      = {{ASTRONOMY & ASTROPHYSICS}},
  keywords     = {{polarization,radiative transfer,methods: numerical,galaxies: nuclei,X-rays: general,ACTIVE GALACTIC NUCLEI,CARLO RADIATIVE-TRANSFER,SUBARCSECOND MIDINFRARED VIEW,BLACK-HOLE MASS,UV POLARIZATION,SPECTRAL MODEL,SEYFERT-GALAXIES,CLUMPY-TORUS,POLAR DUST,POLARIMETRIC SIGNATURES}},
  language     = {{eng}},
  pages        = {{16}},
  title        = {{X-ray polarisation in AGN circumnuclear media : polarisation framework and 2D torus models}},
  url          = {{http://doi.org/10.1051/0004-6361/202450773}},
  volume       = {{689}},
  year         = {{2024}},
}

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