Special Features of Galactic Dynamics

Abstract

This is an introductory article to some basic notions and currently open problems of galactic dynamics. The focus is on topics mostly relevant to the so-called ‘new methods’ of celestial mechanics or Hamiltonian dynamics, as applied to the ellipsoidal components of galaxies, i.e., to the elliptical galaxies and to the dark halos and bulges of disk galaxies. Traditional topics such as Jeans theorem, the role of a ‘third integral’ of motion, Nekhoroshev theory, violent relaxation, and the statistical mechanics of collisionless stellar systems are ?rst discussed. The emphasis is on modern extrapolations of these old topics. Recent results from orbital and global dynamical studies of galaxies are then shortly reviewed. The role of various families of orbits in supporting self-consistency, as well as the role of chaos in galaxies, are stressed. A description is then given of the main numerical techniques of integration of the N-body problem in the framework of stellar dynamics and of the results obtained via N-Body experiments. A ?nal topic is the secular evolution and selforganization of galactic systems.KeywordsElliptical GalaxyChaotic OrbitRegular OrbitHubble TimeSecular EvolutionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.