Computer Science
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd..14e..20g&link_type=abstract
Modelling Dense Stellar Systems, 26th meeting of the IAU, Joint Discussion 14, 22-23 August 2006, Prague, Czech Republic, JD14,
Computer Science
Scientific paper
Introduction: It was Oort in 1957 to point out that the age distribution of open star clusters in the solar neighborhoud was biased towards young clusters. Unless a strong increase in the formation rate of clusters is assumed, it must be a signpost of star cluster disruption. From observations it is possible to determine the typical disruption time of star clusters, which for a 10^4 M[o] cluster was found to be t[4]=1.3 Gyr. Detailed N-body simulations by Baumgardt & Makino (2003), including a realistic mass function, stellar evolution (SEV) and the Galactic tidal field, find t[4]=6 Gyr, i.e. not able to reproduce the age distribution of open clusters. Methods: We performed N-body simulations of encounters between spiral arms and clusters and giant molecular clouds (GMCs) and clusters. The spiral arms and GMCs are modeled by a time dependent analytical potential. We compare the energy gain of the cluster after various types of encounters and compare with analytical work of, for example, Spitzer. Results: For the GMCs we find good agreement between the results of Spitzer for distant encounters and our N-body simulations. We extend the analytical predictions to close and head-on encounters and compare again with N-body simulations. Although the energy gain agrees well with the analytical work, we show that injecting enough energy to bring the cluster energy to zero, does not unbind a star cluster. In stead, the mass loss is the important parameter. We use the mass loss following from the simulations and observational constraints on GMC density and spiral arm parameters, to express the total mass loss by external perturbations (GMCs + spiral arms) in the solar neighborhood. Discussion: The mass loss result of our study is combined with analytical expressions for the mass loss due to the tidal field and SEV and we can reproduce the age distribution of Galactic open clusters with good accuracy.
Gieles Mark
Lamers Henny J. G. L. M.
Portegies Zwart Simon
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