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Dynamical Age Determination of Open Clusters

Published online by Cambridge University Press:  14 August 2015

M. Buchholz  and
Th. Schmidt-Kaler
M. Buchholz
Affiliation:
Astronomisches Institut der Ruhr-Universität Bochum, Germany F. R.
Th. Schmidt-Kaler
Affiliation:
Astronomisches Institut der Ruhr-Universität Bochum, Germany F. R.

Extract

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The radial mass distribution (obtained by counting stars in strips) of the real cluster is compared successively to the distribution functions of a simulated cluster of 100 stars, each of which corresponds to a certain dynamical age, Tdyn, The value of Tdyn, belonging to the function most similar to the observed one is taken to be the dynamical age of the cluster. The radius is given in units of R1/2 (sphere containing half of the total mass); this unit is nearly time-independent. The difference between the distribution functions is measured by the maximum Δmax of the Kolmogorov-Smirnov test which is free from assumptions on the form of the distributions. The minimum in the plot Δmax vs Tdyn, indicates the age of the cluster. It is then converted into an absolute age, Tabs (in years), by The error due to the dynamical theory (limited number of distribution functions, etc.) is estimated at 12%, the error due to the uncertainty of diameter and mass of the cluster is about 30%. Unreliable results were obtained in case of strongly inhomogeneous reddening of the cluster. As an example, the plot of the test values for NGC 457 is given in Figure 1.

Type
August 28 Open Clusters
Information
Symposium - International Astronomical Union , Volume 85: Star Clusters , 1980 , pp. 221 - 222
Copyright
Copyright © Reidel 1980