SCYON Abstract

Received on December 4 2010

Calibration of radii and masses of open clusters with a simulation

Authors	Ernst A. (¹), Just A. (¹), Berczik P. (^1,2,3), and Petrov M. I. (⁴)
Affiliation	(¹) Astronomisches Rechen-Institut am Zentrum für Astronomie der Univ. Heidelberg (²) National Astronomical Observatories of China, Beijing (³) Main Astronomical Observatory, National Academy of Sciences of Ukraine, Kyiv (⁴) Institut für Astronomie der Universität Wien
Accepted by	Astronomy & Astrophysics
Contact	aernst@ari.uni-heidelberg.de
URL	http://arxiv.org/abs/1009.0710
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Abstract

Context: A recent new approach to apply a simple dynamical mass estimate of tidally limited star clusters is based on the identification of the tidal radius in a King profile with the dynamical Jacobi radius. The application to an unbiased open cluster catalogue yields significantly higher cluster masses compared to the classical methods.
Aims: We quantify the bias in the mass determination as function of projection direction and cluster age by analysing a simulated star cluster.
Methods: We use direct N-body simulations of a star cluster including stellar evolution in an analytic Milky Way potential and apply a best fit to the projected number density of cluster stars.
Results: We obtain significantly overestimated star cluster masses which depend strongly on the viewing direction. The overestimation is typically in the range of 10-50 percent and reaches a factor of 3.5 for young clusters. Mass segregation reduces the derived limiting radii systematically.