Star Cluster Life-times: Dependence on Mass, Radius and Environment

The dissolution time (tdis) of clusters in a tidal field does not scale with the “classical” expression for the relaxation time. First, the scaling with N, and hence cluster mass, is shallower due to the finite escape time of stars. Secondly, the cluster half-mass radius is of little importance. Thi...

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Bibliographic Details
Published in:Proceedings of the International Astronomical Union 2007-09, Vol.3 (S246), p.171-175
Main Authors: Gieles, Mark, Lamers, Henny J. G. L. M., Baumgardt, Holger
Format: Article
Language:English
Subjects:
Astronomy
Astrophysics
Contributed Papers
Dissolution
Field strength
Galactic clusters
Galaxies
Molecular clouds
Molecular gases
Perturbation
Relaxation time
Simulation
Star & galaxy formation
Star clusters
Stars & galaxies
Stellar evolution
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Summary:The dissolution time (tdis) of clusters in a tidal field does not scale with the “classical” expression for the relaxation time. First, the scaling with N, and hence cluster mass, is shallower due to the finite escape time of stars. Secondly, the cluster half-mass radius is of little importance. This is due to a balance between the relative tidal field strength and internal relaxation, which have an opposite effect on tdis, but of similar magnitude. When external perturbations, such as encounters with giant molecular clouds (GMC) are important, tdis for an individual cluster depends strongly on radius. The mean dissolution time for a population of clusters, however, scales in the same way with mass as for the tidal field, due to the weak dependence of radius on mass. The environmental parameters that determine tdis are the tidal field strength and the density of molecular gas. We compare the empirically derived tdis of clusters in six galaxies to theoretical predictions and argue that encounters with GMCs are the dominant destruction mechanism. Finally, we discuss a number of pitfalls in the derivations of tdis from observations, such as incompleteness, with the cluster system of the SMC as particular example.
ISSN:1743-9213
1743-9221
DOI:10.1017/S1743921308015536