The AGN Obsuring Torus

The generally held view of active galactic nuclei (AGN) is that of a supermassive black hole surrounded by an obscuring toroidal structure, with much of the AGN observed diversity simply explained as the result of viewing this axisymmetric geometry from different angles. The torus consists of a large number of individually very optically thick dusty clouds which absorb a fraction of the nuclear luminosity and re-radiate it in infrared. However, because of theoretical difficulties, models of the torus IR emission traditionally employed smooth density distributions. We have recently developed the basic formalism for handling dusty cloud distributions, and our clumpy torus models have already been utilized successfully in analysis of Spitzer observations. This proposal requests support for the implementation of a full treatment of the dust grain mixture in our torus model calculations. From the results we will find the variation in dust composition and abundance in clouds across the interface between the torus and the broad lines region, and provide detailed model predictions for the reverberation response in near-IR and emission line spectrum. This will open up a new type of analysis, in which Spitzer observations are combined with reverberation measurements to shed light on the origin and dynamics of clouds around the AGN central black-hole. The results ofthis proposal will be incorporated into a web site that enables users to fit IR observations with clumpy torus models with their own sets of input parameters.