The Flow through the Arms of Normal and Barred-Spiral Galaxies

We examine the flow at the arms of spiral galaxies from a qualitative point of view. In particular we investigate the properties in cases of ordered and chaotic stellar flows. Ordered flows are associated with normal (non-barred) spiral galaxies, while chaotic arms appear in barred-spiral systems. The two cases are characterized by different forcing at corotation. The chaotic orbits that reinforce the spiral arms traverse also the bar region and are associated with the outer boxy isophotes surrounding early type bars. Chaotic spiral arms either stop at an azimuth smaller than pi/2, or present clear gaps at this angle.