Orbital dynamics of three-dimensional bars - II. Investigation of the parameter space

Abstract

We investigate the orbital structure in a class of three-dimensional (3D) models of barred galaxies. We consider different values of the pattern speed, of the strength of the bar and of the parameters of the central bulge of the galactic model. The morphology of the stable orbits in the bar region is associated with the degree of folding of the x 1 characteristic. This folding is larger for lower values of the pattern speed. The elongation of rectangular-like orbits belonging to x 1 and to x 1-originated families depends mainly on the pattern speed. A detailed investigation of the trees of bifurcating families in the various models shows that major building blocks of 3D bars can be supplied by families initially introduced as unstable in the system, but becoming stable at another energy interval. In some models without radial and vertical 2:1 resonances we find, except for the x 1 and x 1-originated families, also families related to the z-axis orbits, which support the bar. Bifurcations of the x 2 family can build a secondary 3D bar along the minor axis of the main bar. This is favoured in the slowly rotating bar case.