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http://dx.doi.org/10.5303/JKAS.2002.35.2.087

DYNAMICAL EVOLUTION IN THE OPEN CLUSTER NGC 6819  

KANG YaNG-WOO (Department of Earth Sciences, Pusan National University)
ANN HONG BAE (Department of Astronomy, Yonsei University)
Publication Information
Journal of The Korean Astronomical Society / v.35, no.2, 2002 , pp. 87-95 More about this Journal
Abstract
We have conducted VI CCD photometry of the open cluster NGC 6819 in order to understand the effects of dynamical evolution in old open clusters. Our photometry covers 18' $\times$ 18' on the sky, centered on the cluster, which seems to cover the whole cluster field. Our photometry reaches down to V $\approx$ 20.5, which allows us to analyze the luminosity function and spatial distribution of stars brighter than Mv $\approx$ 8.5. There is a clear evidence for mass segregation in NGC 6819, i.e., the giants and upper main-sequence stars are concentrated in the inner regions, whereas the lower main-sequence stars distribute almost uniformly throughout the cluster. The luminosity function of the main-sequence stars of NGC 6819 is almost flat. The flat luminosity function indicates that a large number of low mass stars has escaped from the cluster unless its initial mass function is much different from the Salpeter type (${\phi}(m){\propto} m^{-(1+x)},x = 1.35$).
Keywords
open clusters; individual (NGC6819); luminosity function; mass function;
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