AST 552 Galactic Dynamics

Credit Hours: 4
Prerequisite: AST 461, AST 462 or AST 465

Boltzmann equation and collision theory. Structure and evolution of clusters, numerical experiments, Galactic hydrodynamics, wave theory of spiral arms, models of galactic nucleus regions, superdense cluster theory.

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syllabus

1. Review. The observed stellar distribution functions. Local standard(s) of rest. Classic integrals of motion; Lagrange's identity; the virial theorem. The motions of stars in nearly steady state axisymmetric gravitational potentials; first order perturbation theory.
2. The theoretical stellar distribution function. Collision times. Liouville's theorem. Chandresekhar's theorem for ellipsoidal distributions. Hydrodynamic approximation (the Jeans equations). Tidal friction.
3. Representations of galactic potentials. Useful solutions of Poisson's equation. The self-consistency problem.
4. Galactic disk density wave theory. The Lin-Shu theory. Toomre's extension.
5. Instabilities of gravitational systems. The Jeans problem. Antonov's theorems. Disk instabilities and the need for a massive halo.
6. Cluster Stability. Cluster evaporation. The impulse approximation. Slow encounters. Expansion vs. contraction. Internal cluster structure.
7. Entropy considerations. Specific heat instability. No global entropy maximum. Violent relaxation. The gravothermal catastrophe.
8. Numeric approaches to relaxation problems and collisions between systems. Dark matter.
9. Miscellaneous. The gas flow problem: the Galactic fountain. The galaxy formation problem. Suggested modifications of Newtonian gravitational theory.

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