A Physical Model for a Radiative, Convective Dusty Disk in AGN

Abstract

Abstract An accretion disk in an Active Galactic Nucleus harbors and shields dust from external illumination. Our model shows that, at the midplane of the disk around an M BH = 107 M ⊙ black hole, dust can exist at 0.1 pc from the black hole, compared to 0.5 pc outside of the disk where such self-shielding is constrained. We construct a physical model of a disk region approximately located between the radius of dust sublimation at the disk midplane and the radius at which dust sublimes at the disk surface. Our main conclusion is that, for a wide range of model parameters such as local accretion rate and/or opacity, the accretion disk’s own radiation pressure on dust significantly influences its vertical structure. In this region, convection plays important role in the vertical transport of energy. When the local accretion rate exceeds 2.5M ⊙ yr, the 10−2 pc scale disk is supercritical with respect to dust opacity. Such a disk puffs up and transforms from geometrically thin to slim. Our model fits into the narrative of a “failed wind” scenario of Czerny & Hryniewicz and the “compact torus” model of Baskin & Laor, incorporating them as variations of the radiative dusty disk model.