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- Title
The Centaurus I cluster of galaxies - An extreme case of contamination?
- Authors
Lucey, J. R.; Dickens, R. J.; Dawe, J. A.
- Abstract
Although the virial theorem is often used to calculate a system's mass from its size and velocity dispersion, there is considerable uncertainty over the result because of the problem of defining the true membership of the system. Recent analysis1 of hypothetical galaxy systems in model universes has indicated that this local contamination can cause large errors in virial mass estimates for rich clusters. Non-member galaxies projected in the line of sight onto clusters are not easily recognized, unless they have redshifts significantly different from the cluster mean redshift. Contaminating galaxies more local to the cluster (for example, those with a small redshift difference) will be hidden in the large intrinsic motions of the cluster members. Other difficulties associated with application of the virial theorem include possible substructure within the clusters and non-virial motions (for example, infall or expansion). Such effects obscure the physical meaning of a derived virial mass. Here we emphasize the reality of these problems, as evidenced by the resolution of the Centaurus I cluster of galaxies into two distinct velocity systems, based on extensive new redshift data2.
- Publication
Nature, 1980, Vol 285, Issue 5763, p305
- ISSN
0028-0836
- Publication type
Article
- DOI
10.1038/285305a0