Astron. Astrophys. 334, 381-387 (1998)

3. How the collapse time depends on the dynamical friction

Like DG97, we have solved Eq. (7) numerically and calculated the collapse time for different values of the dynamical friction coefficent . However, DG97 showed the dependence of on qualitatively, whilst we have found also an analytical relation that links with in the range of values (see also Gambera 1997). The results of our calculations are shown in Fig. 5, where we report the collapse time versus the dynamical friction coefficient. We have determined the function through a least squares fit method. Our best solution is given by:

with:

Eq. (21) and our results for from the numerical integration of Eq. (7) are in excellent agreement. As a matter of fact, the correlation coefficient value obtained is: .

Fig. 5. Collapse time of a shell of matter made of galaxies and substructure when dynamical friction is taken into account, versus .

© European Southern Observatory (ESO) 1998

Online publication: May 15, 1998

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