Book contents
- Frontmatter
- Contents
- Preface
- Introduction
- Part I Idealized homogeneous systems – basic ideas and gentle relaxation
- Part II Infinite inhomogeneous systems – galaxy clustering
- Part III Finite spherical systems – clusters of galaxies, galactic nuclei, globular clusters
- Part IV Finite flattened systems – galaxies
- 56 Observed dynamics of galaxies
- 57 Kinematics of motion
- 58 Transfer of angular momentum
- 59 Rotation curves and galaxy mass
- 60 Orbits and third integrals
- 61 Axisymmetric and bar instabilities
- 62 Spiral instabilities
- 63 Triaxial and irregular systems
- 64 Gravitational shocks
- 65 Passing–merging
- 66 Problems and extensions
- 67 Unanswered questions
- 68 Bibliography
- Index
56 - Observed dynamics of galaxies
Published online by Cambridge University Press: 05 July 2011
- Frontmatter
- Contents
- Preface
- Introduction
- Part I Idealized homogeneous systems – basic ideas and gentle relaxation
- Part II Infinite inhomogeneous systems – galaxy clustering
- Part III Finite spherical systems – clusters of galaxies, galactic nuclei, globular clusters
- Part IV Finite flattened systems – galaxies
- 56 Observed dynamics of galaxies
- 57 Kinematics of motion
- 58 Transfer of angular momentum
- 59 Rotation curves and galaxy mass
- 60 Orbits and third integrals
- 61 Axisymmetric and bar instabilities
- 62 Spiral instabilities
- 63 Triaxial and irregular systems
- 64 Gravitational shocks
- 65 Passing–merging
- 66 Problems and extensions
- 67 Unanswered questions
- 68 Bibliography
- Index
Summary
examine this region of short distances and definite places
W. H. AudenHistory has shown that the Universe is complex. The more closely we examine astronomical systems the more branches of physical theory we need to understand their behavior and origin, and the more we must specialize the general theory of the last three parts to apply to particular systems. Passing through this book we have successively examined systems of decreasing symmetry. In Part II we dropped the homogeneity that dominated Part I. In Part III we dropped the infinite boundaries that dominated Part II. Now, in Part IV, we are about to drop the spherical symmetry that dominated Part III. As a result there is less to say of a general nature. To compensate, there arises a richness of detail which can often be compared with observations. Although such comparisons are not within the scope of this book, a sketch of some basic observed dynamical properties of non-spherical systems helps give a useful perspective.
In forming impressions of galactic structure we must be especially careful of selection effects. These influence what we observe in subtle ways. Rates of extragalactic information flow are slow, and the natural desire to get interesting results from long nights spent observing often subconsciously affects the choice of objects and places to examine. Versatile and sensitive detectors continue to improve this situation.
On a more fundamental level the brightness of the night sky limits our vision.
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- Gravitational Physics of Stellar and Galactic Systems , pp. 399 - 405Publisher: Cambridge University PressPrint publication year: 1985