Galaxy Orbits for Galaxy Clusters in Sloan Digital Sky Survey and 2dF Galaxy Redshift Survey

摘要

We present the results of a study for galaxy orbits in galaxy clusters usinga spectroscopic sample of galaxies in Sloan Digital Sky Survey (SDSS) and 2dFGalaxy Redshift Survey (2dFGRS). We have determined the member galaxies ofAbell clusters covered by these surveys using the galaxies' redshift andpositional data. We have selected 10 clusters using three criteria: the numberof member galaxies is greater than or equal to 40, the spatial coverage iscomplete, and X-ray mass profile is available in the literature. We derive theradial profile of the galaxy number density and velocity dispersion using all,early-type, and late-type galaxies for each cluster. We have investigated thegalaxy orbits for our sample clusters with constant and variable velocityanisotropies over the clustercentric distance using Jeans equation. Using allmember galaxies, the galaxy orbits are found to be isotropic within theuncertainty for most of sample clusters, although it is difficult to concludestrongly for some clusters due the large errors and the variation as a functionof the clustercentric distance in the calculated velocity anisotropies. Weinvestigated the orbital difference between early-type and late-type galaxiesfor four sample clusters, and found no significant difference between them.