Structure and dynamics of 3D N-body barred galaxies.
Abstract
A detailed study of 3D stable, self-gravitating and rotating N-body barred galaxies is presented. Static and evolutionary descriptions are considered. In order to gain insight into the intricate dynamics taking place in bars, the models are examined at four levels: 1) global shape and kinematics, 2) potential and resonances, 3) periodic orbits and their stability, and 4) phase space occupation by the particles. We find that the vertical resonances in the bar can act as an efficient vertical heating mechanism. The box-peanut shapes are generated by the vertical ILR (2/1 resonance) and a temporary symmetry breaking in z. Outside the bar, an exponential disc gradually forms with the only influences of gravitational forces and bar presence. The potential and the particle distribution are characterised by several a priori improbable features, such as marginal stability of the Lagrangian points, or a pattern speed just large enough to prevent a radial ILR. Asymmetries, both radial and vertical, influence the evolution of the orbital structure and the model's features. The bar shape is sustained by the direct B (or x_1_) orbit family, which has a small vertical instability strip (2/1 resonance) leading to bifurcations onto the so-called banana and anti- banana orbit families. The retrograde R (or x_4_) orbit family has an extended vertical instability strip (1/1 resonance) leading to bifurcation onto the anomalous orbit families. The number of retrograde stars tends to increase with time. Inside the corotation radius, more than half of the initial angular momentum is ejected. For single particles the time-scale of the angular momentum exchange is about half the bar rotation period. Particles can be separated into three distinct kinematical components, a bar, a disc, and a hot component. This decomposition is distinct from the common morphological decomposition of observed barred galaxies in bulge, bar and disc components.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 1991
- Bibcode:
- 1991A&A...252...75P
- Keywords:
-
- Barred Galaxies;
- Galactic Structure;
- Many Body Problem;
- Galactic Rotation;
- Lagrangian Equilibrium Points;
- Orbital Elements;
- Orbital Resonances (Celestial Mechanics);
- Astrophysics