Non radial motions and the shapes and the abundance of clusters of galaxies

TL;DR

This paper investigates how non-radial motions influence the mass function, velocity dispersion function, and shapes of galaxy clusters, showing improved agreement with observations and less elongated clusters compared to standard CDM models.

Contribution

It introduces a model incorporating non-radial motions that better matches observational data on galaxy clusters' properties and shapes.

Findings

Non-radial motions reduce discrepancies between CDM predictions and observations.

Model predictions align well with observational data for mass and velocity dispersion functions.

Non-radial motions lead to less elongated galaxy clusters, consistent with observed shapes.

Abstract

We study the effect of non-radial motions on the mass function, the velocity dispersion function (hereafter VDF) and on the shape of clusters of galaxies using the model introduced in Del Popolo & Gambera (1998a,b; 1999). The mass function of clusters, obtained using the quoted model, is compared with the statistical data by Bahcall & Cen (1992a,b) and Girardi et al. (1998), while the VDF is compared with the Center for Astrophysics (hereafter CfA) data by Zabludoff et al. (1993) for local clusters and those of Mazure et al. (1996) and Fadda et al. (1996). In both cases the model predictions are in good agreement with the observational data showing once more how non-radial motions can reduce many of the discrepancies between Cold Dark Matter (hereafter CDM) model predictions and observational data. Finally we study the effect of non-radial motions on the intrinsic shape of clusters of galaxies showing that non-radial motions produce clusters less elongated with respect to CDM model in agreement with de Theije et al. (1995, 1997) results.