Substructure effects on the collapse of density perturbations

TL;DR

This paper numerically investigates how substructure and dynamical friction influence the collapse of density perturbations in galaxy clusters, revealing that increased clustering and dynamical friction slow down collapse and affect collapse times.

Contribution

It introduces a numerical analysis of substructure effects on perturbation collapse, incorporating dynamical friction coefficients for clustered and unclustered scenarios, which was not previously detailed.

Findings

Dynamical friction slows down the collapse of matter shells.

Collapse time increases with higher dynamical friction coefficients.

Clustering amplifies the effect of dynamical friction on collapse dynamics.

Abstract

We solve numerically the equations of motion for the collapse of a shell of baryonic matter, made of galaxies and substructure of $ 10^{6} M_{\odot}- 10^{9} M_{\odot}$, falling into the central regions of a cluster of galaxies taking account of dynamical friction. We calculate the evolution of the expansion parameter, a(t), of the perturbation using a coefficient of dynamical friction, $ \eta_{0}$, calculated for a perturbation in which clustering is absent and a coefficient $ \eta_{cl}$ obtained from a clustered one. The effect of the dynamical friction is to slow down the collapse (V. Antonuccio-Delogu \& S. Colafrancesco 1994, hereafter AC) producing an observable variation of the parameter of expansion of the shell. The effect increases with increasing $ \eta $ and with the increasing of clustering. Finally, we show how the collapse time depends on $ \eta_{0}$ and $ \eta_{cl}$. keywords: {cosmology: theory- galaxies: formation}