MULTI-PHASE NATURE OF A RADIATION-DRIVEN FOUNTAIN WITH NUCLEAR STARBURST IN A LOW-MASS ACTIVE GALACTIC NUCLEUS

The structures and dynamics of molecular, atomic, and ionized gases are studied around a low-luminosity active galactic nucleus (AGN) with a small () black hole using three-dimensional (3D) radiation–hydrodynamic simulations. We studied, for the first time, the non-equilibrium chemistry for the X-ray-dominated region in the "radiation-driven fountain" with supernova feedback. A double hollow cone structure is naturally formed without postulating a thick "torus" around a central source. The cone is occupied with an inhomogeneous, diffuse ionized gas and surrounded by a geometrically thick () atomic gas. Dense molecular gases are distributed near the equatorial plane, and energy feedback from supernovae enhances their scale height. Molecular hydrogen exists in a hot phase (>1000 K) as well as in a cold (), dense () phase. The velocity dispersion of H2 in the vertical direction is comparable to the rotational velocity, which is consistent with near-infrared observations of nearby Seyfert galaxies. Using 3D radiation transfer calculations for the dust emission, we find polar emission in the mid-infrared band (12 μm), which is associated with bipolar outflows, as suggested in recent interferometric observations of nearby AGNs. If the viewing angle for the nucleus is larger than 75°, the spectral energy distribution is consistent with that of the Circinus galaxy. The multi-phase interstellar medium observed in optical/infrared and X-ray observations is also discussed.