2005/11/30 by Ewa L. Łokas, Ewa L. Lokas, Radoslaw Wojtak +6 · 10 citations
Environmental Science · Physics and Astronomy · #Galaxies: Formation, Evolution, Phenomena #Impact of Light on Environment and Health #Remote Sensing in Agriculture #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2006.10151.x
published as Mon.Not.Roy.Astron.Soc.367:1463-1472,2006 · 11 pages, 9 figures, final version accepted for publication in MNRAS
arxiv created 2005/12/20 · openalex publication_date 2006/03/14 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We study the mass distribution in six nearby (z < 0.06) relaxed Abell clusters of galaxies A0262, A0496, A1060, A2199, A3158 and A3558. Given the dominance of dark matter in galaxy clusters, we approximate their total density distribution by the Navarro, Frenk & White (NFW) formula characterized by virial mass and concentration. We also assume that the anisotropy of galactic orbits is reasonably well described by a constant and that galaxy distribution traces that of the total density. Using the velocity and position data for 120–420 galaxies per cluster we calculate, after removal of interlopers, the profiles of the lowest order even velocity moments, dispersion and kurtosis. We then reproduce the velocity moments by jointly fitting the moments to the solutions of the Jeans equations. Including the kurtosis in the analysis allows us to break the degeneracy between the mass distribution and anisotropy and constrain the anisotropy as well as the virial mass and concentration. The method is tested in detail on mock data extracted from the N-body simulations of dark matter haloes. We find that the best-fitting Galactic orbits are remarkably close to isotropic in most clusters. Using the fitted pairs of mass and concentration parameters for the six clusters, we conclude that the trend of decreasing concentration for higher masses found in the cosmological N-body simulations is consistent with the data. By scaling the individual cluster data by mass, we combine them to create a composite cluster with 1465 galaxies and perform a similar analysis on such sample. The estimated concentration parameter then lies in the range 1.5 < c < 14 and the anisotropy parameter in the range −1.1 < β < 0.5 at the 95 per cent confidence level.