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Session 116 - Large Scale Structure.
Oral session, Thursday, January 16
Piers 4/5,

[116.04] The Pairwise Velocity Dispersion of Galaxies in the Century Survey

R. O. Marzke (DAO), M. J. Geller, D. Fabricant, M. Kurtz, E. Falco, J. P. Huchra (Harvard University), J. Thorstensen, G. Wegner (Dartmouth)

The pairwise velocity dispersion of field galaxies is often held up as one of the strongest constraints on models of structure formation such as CDM. The dispersion measured by Davis and Peebles (1983), 340\pm40 km/s, is significantly lower than the dispersion predicted by nearly every variant of CDM. Recently, Zurek et al. 1994, Mo et al. 1993 and Marzke et al. 1995 have reevaluated measurements of the pairwise velocity dispersion in both the data and in the N-body models and have concluded that the measured dispersion is very sensitive to the number of rich clusters in the sample volume. Using a much larger sample of galaxies than Davis and Peebles (1983), Marzke et al. 1995 found that the pairwise velocity dispersion measured from the entire CfA2+SSRS2 survey was significantly larger than earlier measurements: 540 \pm 40 km/s. Marzke et al. also showed that the dispersion dropped to 370\pm60 km/s when rich clusters were excluded from the sample. Here, we compute the pairwise velocity dispersion from the complete, R-selected Century Survey and show that the results are entirely consistent with our earlier measurements from CfA2+SSRS2. This new measurement adds further evidence that the pairwise velocity dispersion, when averaged over all galaxies, is greater than 500 km/s.

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