Orbital Structure and Asymptotic Orbits in Barred-Spiral Galaxies

Using frequency analysis we find the orbital structure of a self-consistent N-body configuration simulating a rotating barred-spiral galaxy. We detect the main families of the regular orbits and of the chaotic ones, separately. Chaotic orbits play a major role in supporting the outer envelope of the bar as well as the ring and the spiral arms. The explanation is given by studying the unstable asymptotic curves of the main unstable periodic orbits of the system. A new type of stickiness phenomenon near the main unstable asymptotic curves on the phase space seems to be responsible for the galaxy's shape outside corotation.