The velocity and mass distribution of clusters of galaxies from the CNOC1 cluster redshift survey

In the context of the CNOC1 cluster survey, redshifts were obtained for galaxies in 16 clusters. The resulting sample is ideally suited for an analysis of the internal velocity and mass distribution of clusters. Previous analyses of this dataset used the Jeans equation to model the projected velocity dispersion profile. However, the results of such an analysis always yield a strong degeneracy between the mass density profile and the velocity dispersion anisotropy profile. Here we analyze the full (R,v) dataset of galaxy positions and velocities in an attempt to break this degeneracy. We build an `ensemble cluster' from the individual clusters under the assumption that they form a homologous sequence. To interpret the data we study a one-parameter family of spherical models with different constant velocity dispersion anisotropy. The best-fit model is sought using a variety of statistics, including the overall likelihood of the dataset. Although the results of our analysis depend slightly on which statistic is used to judge the models, all statistics agree that the best-fit model is close to isotropic. This result derives primarily from the fact that the observed grand-total velocity histogram is close to Gaussian, which is not expected to be the case for a strongly anisotropic model. The best-fitting models have a mass-to-number-density ratio that is approximately independent of radius over the range constrained by the data. They also have a mass-density profile that is consistent with the dark matter halo profile advocated by Navarro, Frenk & White, in terms of both the profile shape and the characteristic scale length. This adds important new weight to the evidence that clusters do indeed follow this proposed universal mass density profile. [Abridged]Comment: 37 pages, LaTeX, with 11 PostScript figures. Accepted by the Astronomical Journal, to appear in the May 2000 issue. This replacement version contains an additional Appendix and one additional Figure with respect to the version submitted to astro-ph originall

Speech Communication

Contains table of contents for Part V, table of contents for Section 1, an introduction, reports on six research projects and a list of publications.C.J. Lebel FellowshipDennis Klatt Memorial FundDigital Equipment CorporationNational Institutes of Health Grant R01-DC00075National Institutes of Health Grant R03-DC01721National Institutes of Health Grant R01-DC01291National Institutes of Health Grant R01-DC00266National Institutes of Health Grant P01-DC00361-06A1National Institutes of Health Contract R01-DC00776National Science Foundation Grant IRI 89-05249National Science Foundation Grant IRI 89-10561National Science Foundation Grant INT 90-2471

Speech Communication

Contains table of contents for Part V, table of contents for Section 1, an introduction, reports on five research projects and a list of publications.C.J. Lebel FellowshipDennis Klatt Memorial FundNational Institutes of Health Grant R01-DC00075National Institutes of Health Grant P01-DC00361-06A1National Institutes of Health Grant R03-DC01721National Institutes of Health Grant R01-DC01291National Institutes of Health Grant R01-DC00261National Institutes of Health Contract R01-DC00776National Science Foundation Grant IRI 89-05249National Science Foundation Grant IRI 89-10561National Science Foundation Grant INT 90-2471