3D Radiation Hydrodynamic Simulations of Gravitational Instability in AGN Accretion Disks: Effects of Radiation Pressure

We perform 3D radiation hydrodynamic local shearing box simulations to study the outcome of gravitational instability (GI) in optically thick Active Galactic Nuclei (AGN) accretion disks. GI develops when Toomre parameter QT \leq 1, and may lead turbulent heating that balances radiative cooling. However, cooling is too efficient, disk undergo runaway fragmentation. In fully gas-pressure-dominated case, we confirm classical result such a thermal balance holds Shakura-Sunyaev viscosity (alpha) due gravitationally-driven turbulence \sim 0.2, corresponding dimensionless times Omega tcool 5. As fraction support by pressure increases, becomes more prone fragmentation, with reduced (increased) critical value alpha (omega tcool). The effect already significant exceeds 10% gas pressure, while radiation-pressure-dominated disks fragment at <50 . latter translates maximum level alpha<0.02, comparable generated Magnetorotational Instability (MRI). Our results suggest gravitationally unstable (QT 1) outer regions AGN (likely for high/near- Eddington rates) should always into stars, perhaps black holes.