02 1 v 1 2 A ug 2 00 4 Morphology of Galactic Open Clusters
نویسنده
چکیده
We analyzed the shapes of Galactic open clusters by the star counting technique with the 2MASS star catalog database. Morphological parameters such as the ellipticity and size have been derived via stellar density distribution, weighed by clustering probability. We find that most star clusters are elongated, even for the youngest star clusters of a few million years old, which are located near to the Galactic disk. The shapes of young star clusters must reflect the conditions in the parental molecular clouds and during the cluster formation process. As an open cluster ages, stellar dynamics cause the inner part of the cluster to circularize, but the overall radius gets larger and the stellar density becomes sparser. We discuss how internal relaxation process competes with Galactic external perturbation during cluster evolution. The way member stars distribute within a star cluster changes as the cluster evolves. The initial stellar distribution is governed by the structure of the parental molecular cloud, and by how star
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