ABSTRACT

The evolution of the gas distribution in a globally unstable galactic disk embedded in a ‘live’ halo is studied numerically on scales ∼ 100 pc –10 kpc. The gas and stars are evolved using a 3D hybrid SPH/N-body code and gravitational interactions are fully accounted for. The gas is assumed to obey the isothermal equation of state with T – 104 K. The effect of a massive object at the disk center is simulated by placing a ‘seed’ black hole (BH) of 5 x 107 M⊙ with an ‘accretion’ radius of 20 pc. Modifications introduced by star formation in the disk are discussed elsewhere (Heller and Shlosman, these proceedings).

We find that the global stability of a stellar disk can be heavily affected by the gas, given that the gas mass fraction fg is high enough and the gas is dissipative. We also find that the rate of radial inflow in disk galaxies is a robust function of global parameters: the inflow is bar-driven for small fg and dynamical friction-driven for largefg. Without star formation the radial inflows lead to (1) domination of the central kpc by a few massive clouds that evolve into a single object via a cloud binary system; and (2) sporadic accretion onto the BH.