Book contents
- Frontmatter
- Contents
- Preface
- Introduction
- Part I Idealized homogeneous systems – basic ideas and gentle relaxation
- Part II Infinite inhomogeneous systems – galaxy clustering
- 20 How does matter fill the Universe?
- 21 Gravitational instability of the infinite expanding gas
- 22 Gravitational graininess initiates clustering
- 23 Growth of the two-galaxy correlation function
- 24 The energy and early scope of clustering
- 25 Later evolution of cosmic correlation energies
- 26 N-body simulations
- 27 Evolving spatial distributions
- 28 Evolving velocity distributions
- 29 Short review of basic thermodynamics
- 30 Gravity and thermodynamics
- 31 Gravithermodynamic instability
- 32 Thermodynamics and galaxy clustering; ξ(r)∝r-2
- 33 Efficiency of gravitational clustering
- 34 Non-linear theory of high order correlations
- 35 Problems and extensions
- 36 Bibliography
- Part III Finite spherical systems – clusters of galaxies, galactic nuclei, globular clusters
- Part IV Finite flattened systems – galaxies
- Index
27 - Evolving spatial distributions
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
- 20 How does matter fill the Universe?
- 21 Gravitational instability of the infinite expanding gas
- 22 Gravitational graininess initiates clustering
- 23 Growth of the two-galaxy correlation function
- 24 The energy and early scope of clustering
- 25 Later evolution of cosmic correlation energies
- 26 N-body simulations
- 27 Evolving spatial distributions
- 28 Evolving velocity distributions
- 29 Short review of basic thermodynamics
- 30 Gravity and thermodynamics
- 31 Gravithermodynamic instability
- 32 Thermodynamics and galaxy clustering; ξ(r)∝r-2
- 33 Efficiency of gravitational clustering
- 34 Non-linear theory of high order correlations
- 35 Problems and extensions
- 36 Bibliography
- Part III Finite spherical systems – clusters of galaxies, galactic nuclei, globular clusters
- Part IV Finite flattened systems – galaxies
- Index
Summary
The curtain of the Universe is rent and shattered, the splendor-winged worlds disperse like wild doves scattered.
ShelleyMany N-body simulations have shown how galaxies disperse and cluster as the universe expands. We shall just examine some representative examples. The 4000-body simulations of Aarseth and his collaborators (see bibliography for references) were designed to see how different initial conditions and cosmological models, within reasonable ranges, alter the clustering of galaxies. Experiments whose initial velocities had a pure Hubble flow behaved much like those which also had peculiar Maxwellian velocities smaller than the expansion velocity. Gravitational graininess built up the self-consistent velocity field after about one initial Hubble expansion in either case.
Somewhat more important is the galaxies' mass distribution. In the computation this does not change with time, although small groups which form can mimic the distant effects of larger mass galaxies at later stages of clustering. Various simulations have shown that the more massive galaxies have a greater tendency to cluster. Their two-point correlation amplitude, for example, increases faster than for less massive galaxies. Linear analysis (Equation (24.1)) leads us to expect this, at least during the initial clustering when the velocity distribution does not depend strongly on mass. Experiments also show that many results, especially regarding spatial distribution, do not depend strongly on detailed properties of the mass spectrum, so long as it continuously spans a range of at least an order of magnitude.
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- Chapter
- Information
- Gravitational Physics of Stellar and Galactic Systems , pp. 185 - 194Publisher: Cambridge University PressPrint publication year: 1985