Chapter accepted to appear in Planets, Stars and Stellar Systems, vol 5, ed G. Gilmore, 2011.
astro-ph/1006.4855

For a PDF version of the article, click here.

DYNAMICS OF DISKS AND WARPS

J.A. Sellwood


Rutgers University, Department of Physics & Astronomy,
136 Frelinghuysen Road, Piscataway, NJ 08854-8019


Abstract: This chapter reviews theoretical work on the stellar dynamics of galaxy disks. All the known collective global instabilities are identified, and their mechanisms described in terms of local wave mechanics. A detailed discussion of warps and other bending waves is also given. The structure of bars in galaxies, and their effect on galaxy evolution, is now reasonably well understood, but there is still no convincing explanation for their origin and frequency. Spiral patterns have long presented a special challenge, and ideas and recent developments are reviewed. Other topics include scattering of disk stars and the survival of thin disks.


Table of Contents

INTRODUCTION

PRELIMINARIES
Relaxation Rate
Mathematical Formulation
Orbits
Resonances
Wave-Particle Scattering
Vertical Motion

LOCAL THEORY OF DENSITY WAVES
Plane Waves in a Thin Mass Sheet
Dispersion Relations
Axisymmetric Stability
Self-consistent Density Waves
Group Velocity
Swing Amplification

BAR INSTABILITY
Mechanism for the Bar Mode
Predicted Stability
Residual Concerns

LOP-SIDED MODES

GROOVE AND EDGE MODES

SPIRAL STRUCTURE
Spirals as Global Modes of Smooth Disks
Recurrent Transients
Spirals as Responses to Density Fluctuations
Non-linear Spiral Dynamics
Spirals in Global N-body Simulations
A Recurrent Instability Cycle?

BUCKLING INSTABILITIES AND WARPS
Local Theory of Bending Waves
Global Bending Modes
Simulations of Buckling Modes
Disks in Halos
Misaligned Infall
Warps Driven by Tides

BARS
Origin of Bars
Frequency of Bars
Structure of Bars
Gas Flow
Bar Pattern Speeds
Bars Within Bars
Buckling of Bars
Dynamical Friction on Bars

SECULAR EVOLUTION WITHIN DISKS
Heating by Spirals
Churning by Transient Spirals
Cloud Scattering
Black Holes in the Halo
Discussion

FRAGILITY OF DISKS

CONCLUSIONS

REFERENCES

APPENDIX: RELAXATION TIME IN SPHEROIDS AND DISKS

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