Substructure effects on the collapse of density perturbations
Abstract
Description
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, $ η_{0}$, calculated for a perturbation in which clustering is absent and a coefficient $ η_{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 $ η$ and with the increasing of clustering. Finally, we show how the collapse time depends on $ η_{0}$ and $ η_{cl}$. keywords: {cosmology: theory- galaxies: formation}
5 pages + 3 PostScript figures, Latex (use laa.sty), accepted for the pubblication in Astr. and Astrop
5 pages + 3 PostScript figures, Latex (use laa.sty), accepted for the pubblication in Astr. and Astrop