W.P. Chen, C.W. Chen (NCU), C.G. Shu (ShAO)
Thirty-six open clusters were selected from the 2MASS database on the basis of the latest open cluster catalogue (Dias et al 2002). Morphological parameters such as the ellipticity, orientation were derived by isodensity elliptic fitting of local stellar density. Most star clusters are found to be elongated with the ellipticity correlated inversely with the height above the Galactic plane. The morphology shows clear evidence of progressively more tidal distortion toward the outer parts of a star cluster. We show how internal dynamics and external disturbances compete to govern the dynamical structure of a star cluster after ~ 100 Myr.
This work has been supported in part by grants NSC91-2112-M-008-036 and NSC91-2112-M-008-043.