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
- 37 Breakaway
- 38 Violent relaxation
- 39 Symmetry and Jeans' theorem
- 40 Quasi-equilibrium models
- 41 Applying the virial theorem
- 42 Observed dynamical properties of clusters
- 43 Gravithermal instabilities
- 44 Self-similar transport
- 45 Evaporation and escape
- 46 Mass segregation and equipartition
- 47 Orbit segregation
- 48 Binary formation and cluster evolution
- 49 Slingshot
- 50 Role of a central singularity
- 51 Role of a distributed background
- 52 Physical stellar collisions
- 53 More star–gas interactions
- 54 Problems and extensions
- 55 Bibliography
- Part IV Finite flattened systems – galaxies
- Index
53 - More star–gas interactions
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
- 37 Breakaway
- 38 Violent relaxation
- 39 Symmetry and Jeans' theorem
- 40 Quasi-equilibrium models
- 41 Applying the virial theorem
- 42 Observed dynamical properties of clusters
- 43 Gravithermal instabilities
- 44 Self-similar transport
- 45 Evaporation and escape
- 46 Mass segregation and equipartition
- 47 Orbit segregation
- 48 Binary formation and cluster evolution
- 49 Slingshot
- 50 Role of a central singularity
- 51 Role of a distributed background
- 52 Physical stellar collisions
- 53 More star–gas interactions
- 54 Problems and extensions
- 55 Bibliography
- Part IV Finite flattened systems – galaxies
- Index
Summary
And all dishevelled wandering stars
W.B. YeatsGalactic winds
Stellar collisions, novae, supernovae, planetary nebulae, stellar winds and flares all dump gas into a star cluster or galaxy. How much of this gas cools and remains in the cluster, and how much escapes is a fundamental question. The answer is difficult because it depends completely on details of the mass loss process and on the subsequent interactions of gas lost from different stars. Clouds may collide and the heat generated by shocks may cause evaporation. Wandering stars may pass through the clouds, heating them as described in Section 17. The results are clearly very model dependent, so we will just consider a very simple example to illustrate the nature of galactic winds. (See Mathews & Baker, 1971, for a detailed analysis.)
A necessary condition for an atom or ion to escape from the cluster is that its energy exceed roughly twice the average energy per atom of the stars' random motions. (The collisional mean free path determines sufficient escape conditions.) If we can average very crudely over the cluster, then supposing that the star and gas motions are in rough energy equipartition (per particle) gives an equivalent escape temperature Tesc≈μν2*/3κ≈2 x 107(μ/0.5)(ν*/1000 km s-1)2 where μ is the mean particle mass in proton units. From Table 6 we see that, in typical systems where the stellar collision time is much less than a Hubble time, gas must be heated to ~ 5 × 107 K.
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- Information
- Gravitational Physics of Stellar and Galactic Systems , pp. 382 - 387Publisher: Cambridge University PressPrint publication year: 1985