Book contents
- Frontmatter
- Contents
- Acknowledgements
- 1 Introduction
- 2 Early history of the dark matter hypothesis
- 3 The stability of disk galaxies: the dark-halo solution
- 4 Direct evidence: extended rotation curves of spiral galaxies
- 5 The maximum-disk: light traces mass
- 6 Cosmology and the birth of astroparticle physics
- 7 Clusters revisited: missing mass found
- 8 CDM confronts galaxy rotation curves
- 9 The new cosmology: introducing dark energy
- 10 An alternative to dark matter: modified Newtonian dynamics
- 11 Seeing dark matter: the theory and practice of detection
- 12 Reflections: a personal point of view
- Appendix Astronomy made simple
- References
- Index
8 - CDM confronts galaxy rotation curves
Published online by Cambridge University Press: 05 July 2014
- Frontmatter
- Contents
- Acknowledgements
- 1 Introduction
- 2 Early history of the dark matter hypothesis
- 3 The stability of disk galaxies: the dark-halo solution
- 4 Direct evidence: extended rotation curves of spiral galaxies
- 5 The maximum-disk: light traces mass
- 6 Cosmology and the birth of astroparticle physics
- 7 Clusters revisited: missing mass found
- 8 CDM confronts galaxy rotation curves
- 9 The new cosmology: introducing dark energy
- 10 An alternative to dark matter: modified Newtonian dynamics
- 11 Seeing dark matter: the theory and practice of detection
- 12 Reflections: a personal point of view
- Appendix Astronomy made simple
- References
- Index
Summary
What do rotation curves require of dark matter?
The extended rotation curves of spiral galaxies are asymptotically flat. This is the essential result of three decades of 21-cm line observations carried out with radio telescopes – single-dish as well as interferometers. Every astronomer and physicist is familiar with this result and its interpretation as visible spiral galaxies being embedded in a more extensive dark halo. But what does this imply about the distribution of dark matter within spiral galaxies? What is required of dark matter in order to explain this essential observation?
In Fig. 8.1 we see again the well-known example of a flat rotation curve, that of the spiral galaxy NGC 2403. This rotation curve has been derived from 21-cm line observations made more than 20 years ago at Westerbork WSRT by Kor Begeman, then a student in Groningen, and it is a clear example of a flat rotation curve which extends well beyond the bright inner regions of the galaxy. Also shown are the combined Newtonian rotation curves of the observable baryonic components of the galaxy – the stars and the gas (assuming that the light traces the mass of the visible disk). The discrepancy between the observations and predictions is very evident in this figure.
In the context of Newtonian dynamics, dark matter must make up this difference between observations and expectations. What sort of dark matter distribution is required in this case?
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- Chapter
- Information
- The Dark Matter ProblemA Historical Perspective, pp. 101 - 118Publisher: Cambridge University PressPrint publication year: 2010