SIMBAD references

We have studied the formation of complex central structures in barred galaxies - nested bars, nuclear spirals and circumnuclear rings - by making N -body simulations, which include the gas component as inelastically colliding particles. Our models suggest that many of the observed features in both the stellar and gas components can be explained by the dynamical effect of two or more modes in the stellar disc. Especially, many morphological features in our simulations correspond to analytically studied orbit loops in double-barred potentials. Interestingly, a fast-rotating secondary bar forms in a purely stellar disc in our simulations, which disagrees with some previous studies where the presence of a dissipative component was needed.