Gas as a tracer of barred spiral dynamics

The gravitational field of a barred spiral galaxy is described by a simple model consisting of two variable components: a central or nuclear disk and a homogeneous triaxial spheroid: and one fixed component: an extended disk or halo. The model is characterized by five free dimensionless parameters: the ratio of bar mass to central disk mass, two axial ratios of the spheroid, the ratio of the central disk length scale to the spheroid semimajor axis, and the corotation radius in units of the spheroid semimajor axis. Two-dimensional, time-dependent gas dynamical calculations are carried out in the gravitational field resulting from this mass model in order to generate a grid of hydrodynamical models on the five-dimensional parameter space. It is found that over a well-defined domain of this parameter space, the steady-state gas density and velocity distributions resemble the observed morphology and kinematics of the gas in actual SBb galaxies