Self-Consistent Models of Barred Spiral Galaxies

Self-consistent models of barred spiral galaxies based on the observed properties of NGC3992, NGC1073, and NGC1398 are constructed and analyzed. The method of model construction is a slight modification of the technique developed by Contopoulos and Grosbol for the case of unbarred spirals. The main factors which influence self-consistency are the amplitude, pitch angle, scale length and z-thickness of the spirals, the mass of the bar, the angular velocity of the bar/spiral pattern, the central surface density and scale length of the disk, and the central value and slope of the velocity dispersion. Stochastic orbits whose Jacobi constants lie between the values at the Lagrange points L 1 and L 4 are found to play a significant role in supporting self-consistent spiral structure, especially in the regions just beyond the ends of the bar. Stochastic orbits whose Jacobi constants lie below this interval tend to fill more or less uniformly either rings in the outer disk or ovals in the bar region, depending on the regions to which they are confined. Stochastic orbits whose Jacobi constants lie above that of L 4 also tend not to support any imposed structure. The model bars are predominantly comprised of elongated orbits trapped around the x 1 family and terminate close to corotation. The response of gas to the forces of the most successful models is calculated using a two-dimensional smoothed particle hydrodynamics code. The results confirm that a bar alone is not sufficient to drive a strong spiral response in the gas of the outer disk. An underlying spiral structure in the more massive stellar component appears to be required. If stellar spirals are present, strong gas spirals may persist for long times.