Studying the Dynamical Properties of 20 Nearby Galaxy Clusters

TL;DR

This study analyzes the dynamical properties of 20 nearby galaxy clusters using SDSS data, applying iterative methods to identify members, fit density profiles, and compare infall velocity models, revealing differences in core and infall region behaviors.

Contribution

It introduces a combined approach using adaptive kernel and spherical infall models to study galaxy cluster dynamics, highlighting the applicability of Yahil and Praton models in different cluster regions.

Findings

Core radii vary from 0.18 to 0.47 Mpc/h with a mean of 0.295 Mpc/h.

Yahil approximation fits outskirts but not cores of clusters.

Praton model describes infall patterns in high-density clusters.

Abstract

Using SDSS-DR7, we construct a sample of 42382 galaxies with redshifts in the region of 20 galaxy clusters. Using two successive iterative methods, the adaptive kernel method and the spherical infall model, we obtained 3396 galaxies as members belonging to the studied sample. The 2D projected map for the distribution of the clusters members is introduced using the 2D adaptive kernel method to get the clusters centers. The cumulative surface number density profile for each cluster is fitted well with the generalized King model. The core radii of the clusters' sample are found to vary from 0.18 Mpc $\mbox{h}^{-1}$ (A1459) to 0.47 Mpc $\mbox{h}^{-1}$ (A2670) with mean value of 0.295 Mpc $\mbox{h}^{-1}$. The infall velocity profile is determined using two different models, Yahil approximation and Praton model. Yahil approximation is matched with the distribution of galaxies only in the outskirts (infall regions) of many clusters of the sample, while it is not matched with the distribution within the inner core of the clusters. Both Yahil approximation and Praton model are matched together in the infall region for about 9 clusters in the sample but they are completely unmatched for the clusters characterized by high central density. For these cluster, Yahil approximation is not matched with the distribution of galaxies, while Praton model can describe well the infall pattern of such clusters.