BAR-DRIVEN FUELING TO A GALACTIC CENTRAL REGION IN A MASSIVE GAS DISC

Using two-dimensional hydrodynamics simulations, we have discovered an effective fuelling process for the central regions of galaxies that have weak bar-like distortions. A gravitational instability of an elongated gas ring at the inner Lindblad resonance (ILR), which has previously been reported as an effective fuelling mechanism, is not needed for the fuelling process we consider here. In our model, a massive gaseous disc in the central region of galaxies responds sensitively to the weakly distorted potential, and a large amount of gas can be fed into within 1/20 of a core radius of the potential in several times 10(7) yr. The ILRs, the dissipative nature of the gas, and the self-gravity of the gas are essential for triggering this effective fuelling. This accumulation process has not previously been described. Specifically, the gas accumulates to form a dense 'linear' structure inclined at about 45 degrees with respect to the bar potential in a leading sense. We also found that a counter-rotating gaseous core could be formed as a result of the fuelling. The sense of the rotation of the core depends on the ratio of the gas mass to the background mass. Physical mechanisms of the fuelling process can be understood using a linear theory of gaseous orbits in a weak barred potential.