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

TL;DR

This study analyzes galaxy orbits in clusters using SDSS and 2dF data, finding mostly isotropic orbits and no significant difference between galaxy types, contributing to understanding galaxy dynamics in clusters.

Contribution

It provides new insights into galaxy orbital anisotropies in clusters using extensive spectroscopic data and Jeans modeling, with a focus on different galaxy types and detailed cluster analysis.

Findings

Galaxy orbits are mostly isotropic within uncertainties.

No significant orbital difference between early-type and late-type galaxies.

Orbit analysis consistent across multiple clusters.

Abstract

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