The Effect of Self-gravity of Gas on Gas Fueling in Barred Galaxies with a Supermassive Black Hole

In our previous paper, we have shown that a gas disk in the nuclear region of a barred galaxy which contains a central supermassive black hole (SMBH) rapidly evolves into a nuclear gas ring by the effect of an additional inner Lindblad resonance caused by the SMBH. In this paper, we investigate the fate of the gas ring, involving self-gravity of gas, using two-dimensional hydrodynamical simulations. We find that the gas ring becomes gravitationally unstable for a gas surface density of gas above a critical value, and fragments into several gas clumps. Some denser clumps increase their mass via the accretion of the surrounding gas and collisions with other clumps, and finally a very massive gas clump (M ∼ 10M⊙) is formed. Due to the torque from the most massive clump, a part of the gas in the ring loses its angular momentum and falls into the galactic center. As a result, a nuclear gas disk (R ∼ 50 pc) is formed around the SMBH. The accretion rate for R < 50 pc attains about 1M⊙ yr −1 for 3.5×10 yr. At the final phase of the bar-driven fueling, self-gravity is crucial for the angular momentum transfer of the gas. This is a new mechanism for gas fueling to the vicinity of the SMBH. Subject headings: galaxies: nuclei – galaxies: starburst – ISM: kinematics and dynamics – methods: numerical