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

Published online by Cambridge University Press:  01 September 2007

Mark Gieles ,
Henny J. G. L. M. Lamers  and
Holger Baumgardt
Mark Gieles
Affiliation:
European Southern Observatory, Casilla 19001, Santiago 19, Chile email: mgieles@eso.org
Henny J. G. L. M. Lamers
Affiliation:
Astronomical Institute, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands email: lamers@astro.uu.nl
Holger Baumgardt
Affiliation:
Argelander Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, Bonn, Germany email: holger@astro.uni-bonn.de
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Abstract

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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.

Keywords

globular clusters: generalopen clusters and associations: generalstellar dynamicsmethods: n-body simulations
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S246: Dynamical Evolution of Dense Stellar Systems , September 2007 , pp. 171 - 175
Copyright
Copyright © International Astronomical Union 2008

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