Colloquium AOB 19-Jun-2024 - An X-ray View on AGN Circumnuclear Media with SKIRT

The next Colloquium of the Astronomical Observatory will be held on Wednesday, June 19, at 12 PM in the Library.

Speaker: Bert Vander Meulen

Topic: An X-ray View on AGN Circumnuclear Media with SKIRT


Active galactic nuclei (AGN) are surrounded by large amounts of cold gas and dust, that reprocess (and obscure) the emission of the central engine. The 3D radiative transfer code "SKIRT" has recently been extended into the X-ray range, to study this circumnuclear medium based on reprocessed X-ray features (Vander Meulen et al. 2023). Furthermore, SKIRT can also model X-ray polarisation (Vander Meulen et al. subm.), providing two additional observables on the AGN circumnuclear medium: the polarisation degree and polarisation angle. The simulation domain of SKIRT now self-consistently covers the X-ray to mm wavelength range, with all features of the established SKIRT framework available.

We used SKIRT to model the parsec-scale circumnuclear medium of Circinus AGN in the X-ray band, adopting a distribution of gas and dust consistent with previous observations in the MIR. This model incorporates the clumpy structure of the polar wind component, X-ray interactions with dust grains, and 3D kinematics, thereby improving upon previous X-ray modelling efforts. Additionally, this SKIRT model can explain the UV-to-IR observations of Circinus AGN (Stalevski et al. 2017, 2019), linking dust modelling to X-ray reprocessing. We compare our model spectra to observational X-ray data from Chandra and NuSTAR, and discuss our model parameters. Finally, we demonstrate how SKIRT can be used to constrain the 3D structure of AGN circumnuclear media with XRISM.

The talk will be recorded and posted on the Observatory's Youtube channel.


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