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Substructure effects on the collapse of density perturbations
A. Del Popolo and
Received 30 October 1996 / Accepted 6 September 1996
We solve numerically the equations of motion for the collapse of a shell of baryonic matter, made of galaxies and substructure of , 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, , calculated for a perturbation in which clustering is absent and a coefficient 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 and with the increasing of clustering. Finally, we show how the collapse time depends on and .
Key words: cosmology: theory galaxies: formation
Send offprint requests to: A. Del Popolo, M. Gambera
Online publication: June 30, 1998