Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgements
- Part I Astronomical background
- 1 High energy astrophysics – an introduction
- 2 The stars and stellar evolution
- 3 The galaxies
- 4 Clusters of galaxies
- Part II Physical processes
- Part III High energy astrophysics in our Galaxy
- Part IV Extragalactic high energy astrophysics
- Appendix: Astronomical conventions and nomenclature
- Bibliography
- Name index
- Object index
- Index
4 - Clusters of galaxies
from Part I - Astronomical background
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Acknowledgements
- Part I Astronomical background
- 1 High energy astrophysics – an introduction
- 2 The stars and stellar evolution
- 3 The galaxies
- 4 Clusters of galaxies
- Part II Physical processes
- Part III High energy astrophysics in our Galaxy
- Part IV Extragalactic high energy astrophysics
- Appendix: Astronomical conventions and nomenclature
- Bibliography
- Name index
- Object index
- Index
Summary
Associations of galaxies range from pairs and small groups, through giant clusters containing over a thousand galaxies, to the vast structures on scales much greater than clusters such as the vast ‘walls’ and voids observed in the distribution of galaxies. Clustering occurs on all scales and very few galaxies can be considered truly isolated. Rich clusters of galaxies are of particular interest because they are the largest gravitationally bound systems in the Universe. The gravitational potential of the cluster is defined by the distribution of dark matter, the mass of which greatly exceeds that of the baryonic matter, such as that contained in the stars in galaxies and the associated interstellar gas and the intracluster gas. The deep gravitational potential wells of clusters can be observed directly through the bremsstrahlung X-ray emission of hot intracluster gas which forms a hydrostatic atmosphere within the cluster. The hot gas can also be detected through the decrements which it causes in the Cosmic Microwave Background Radiation as a result of the Sunyaev–Zeldovich effect. Gravitational lensing has proved to be a very powerful tool for defining the large scale distribution of dark matter in clusters, as well as in individual galaxies within them. Interactions of galaxies with each other and with the intergalactic medium in the cluster can be studied and radio source events can strongly perturb the distribution of hot gas.
- Type
- Chapter
- Information
- High Energy Astrophysics , pp. 99 - 128Publisher: Cambridge University PressPrint publication year: 2011