The second coming of cold dark matter?
While the standard cold dark matter (CDM) model has received numerous marks against it on the basis of a variety of observational data, the prediction of high {Sigma}{Upsilon}, the pairwise-velocity dispersion between galaxies, on small (megaparsec) scales was reported as perhaps one of its greatest failings. Here, we reexamine the case of CDM and {Sigma}{Upsilon}, with high-resolution numerical simulations. The statistic was measured in simulations, in artificial galaxy catalogs, and in the CfA North Forty redshift survey. In our reanalysis of the CfA data, we found that {Sigma}{Upsilon} {approximately} 500 km/s, significantly higher than the original estimates of Davis & Peebles (1983). This new value, along with our estimate of the velocity bias, leads to a virial measure of the cosmological density parameter, {Omega} {approximately} 0.9. which is more than four times the traditionally cited CfA result. Analysis the simulations indicates that while the method of Davis and Peebles works well, the {Sigma}{Upsilon} statistic itself is not generally robust: there is large scatter from catalog to catalog and evidence that the recovered {Sigma}{Upsilon} value depends strongly on a small fraction of galaxies in the central regions of rare, massive clusters. Thus, at present the CDM model cannot be deemed incompatible with observed small-scale peculiar velocities.
- Research Organization:
- Los Alamos National Lab., NM (United States)
- Sponsoring Organization:
- National Aeronautics and Space Administration, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 10115377
- Report Number(s):
- LA-UR-94-4268; CONF-9410287-2; ON: DE95005156
- Resource Relation:
- Conference: 5. astrophysics conference: dark matter,College Park, MD (United States),10-12 Oct 1994; Other Information: PBD: [1994]
- Country of Publication:
- United States
- Language:
- English
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The second coming of cold dark matter?
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