Towards an observationally motivated AGN dusty torus model

Several models of nuclear dust in active galactic nuclei (AGN) have been presented in the literature to determine its physical and geometrical properties, usually assuming the dust density distribution as the main aspect producing differences in the mid-infrared (MIR) emission of AGNs.  My PhD research investigates the physical and chemical properties of dust in the torus of AGNs using MIR spectral analysis and radiative transfer (RT) modeling. First, we determined an observationally motivated dust composition by fitting a mineralogy model to Spitzer/IRS spectra of 49 nearby AGNs showing silicate emission at 10 μm. We found that porous alumina, periclase, and olivine grains of 0.1 μm dominate the fits, while traditional astronomical silicates are rarely favored. Subsequently, we constructed a large RT model grid that explores a parameter space defined by key physical properties of the torus. We focused on the effects of dust density distribution (smooth, clumpy, and two-phase) and dust composition on the MIR spectral energy distribution (SED). The resulting synthetic SEDs were analysed through model-to-model and model-to-observation comparisons. We found that both dust distribution and composition significantly influence the silicate feature strengths and spectral slopes. In this talk, I will present the main results and discuss the principal effects of the density distribution and chemical composition of dust in the MIR SED.