Seminars : Documents

VLT/FORS2 optical imaging polarimetry: the active galactic nucleus in Circinus
Djordje Savic (STAR)

Recent high angular resolution observations resolved for the first time the mid-infrared (MIR) structure of nearby active galactic nuclei (AGN). Surprisingly, a major fraction of their MIR emission comes from the polar regions. This is at odds with the expectation based on AGN unification, which postulates a dusty torus in the equatorial region. An archetype, the Circinus galaxy offers one of the best opportunities for studying the AGN central engine in greater details. The observations were carried out with VLT/FORS2 instrument in optical imaging polarimetry mode operating in U, B, V and R filters. Since polarimetry is highly sensitive to geometric and orientation effects, we built a model for simulating dust scattering. We used the 3D Monte Carlo radiative transfer code SKIRT for obtaining optical polarization maps. The host galaxy foreground extinction as well as the starlight emission was taken into account. Finally, we compare the results of simulations with observations.