The Shape of Velocity Dispersion Profiles and the Dynamical State of Galaxy Clusters

TL;DR

This study examines the velocity dispersion profiles of galaxy clusters to understand their dynamical states, revealing distinct profiles for Gaussian and Non-Gaussian systems and implications for galaxy orbits and infall rates.

Contribution

It introduces a robust classification of cluster dynamical states using Hellinger Distance and analyzes the velocity dispersion profiles for different galaxy populations.

Findings

Gaussian systems show a central peak and decreasing velocity dispersion, indicating radial orbits.

Non-Gaussian systems have a depression in the central VDP and higher infall rates.

Bright galaxies exhibit lower velocity dispersions across all radii.

Abstract

Motivated by the existence of the relationship between the dynamical state of clusters and the shape of the velocity dispersion profiles (VDP), we study the VDPs for Gaussian (G) and Non-Gaussian (NG) systems for a subsample of clusters from the Yang catalog. The groups cover a redshift interval of $0.03\leq z\leq0.1$ with halo mass $\geq 10^{14}$M$_{\odot}$. We use a robust statistical method, Hellinger Distance, to classify the dynamical state of the systems according to their velocity distribution. The stacked VDP of each class, G and NG, is then determined using either Bright or Faint galaxies. The stacked VDP for G groups displays a central peak followed by a monotonically decreasing trend which indicates a predominance of radial orbits, with the Bright stacked VDP showing lower velocity dispersions in all radii. The distinct features we find in NG systems are manifested not only by the characteristic shape of VDP, with a depression in the central region, but also by a possible higher infall rate associated with galaxies in the Faint stacked VDP.