Astronomisches Rechen-Institut Heidelberg

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ARI-Heidelberg Mitteilungen Serie B, No. 27

Author(s): Wielen, R.
Title: The Age Distribution and Total Lifetimes of Galactic Clusters
Source: Astron. Astrophys. 13, 309-322
Year: 1971
Abstract: The age distribution of galactic clusters is obtained from catalogues of well observed clusters compiled by Becker and Fenkart (1971) and Lindoff (1968). The observed age distribution of clusters within 1000 pc does not seem to be seriously affected by selection effects. Assuming a constant rate of formation of clusters, we deduce from the observed age distribution of clusters within 1000 pc statistical information about the total lifetimes of galactic clusters: 50% of new clusters disintegrate within 2 108 years, 10% have a total lifetime longer than 5 108 years, and only 2% live longer than 109 years. Hence, the typical lifetime is short, but there exists a wide spread in the individual lifetimes. The lifetimes obtained in this paper may serve as a powerful observational test of theories of the dynamical evolution of star clusters. We find that only a small fraction of field stars are former members of now dissolved galactic clusters. Moving groups should generally not be identified with disintegrated clusters. The relative dynamical age of a galactic cluster is rather weakly correlated with its absolute age. Therefore, and because of natural selection effects in the surviving old clusters, it is very unlikely that more direct observational information about the dynamical evolution of clusters can be obtained by studying objects of various ages.
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