Regular and chaotic motion in elliptical galaxies

Abstract

Here I review recent work, by other authors and by myself, on some particular topics related to the regular and chaotic motion in elliptical galaxies. I show that it is quite possible to build highly stable triaxial stellar systems that include large fractions of chaotic orbits and that partially and fully chaotic orbits fill different regions of space, so that it is important not to group them together under the single denomination of chaotic orbits. Partially chaotic orbits should not be confused with weakly fully chaotic orbits either, and their spatial distributions are also different. Slow figure rotation (i.e., rotation in systems with zero angular momentum) seems to be always present in highly flattened models that result from cold collapses, with the rotational velocity diminishing or becoming negligibly small for less flattened models. Finally, I comment on the usefulness and limitations of the classification of regular orbits via frequency analysis.