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标题：Stellar Proper Motions in the Orion Nebula Cluster
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作者：Dongwon Kim ; Jessica R. Lu ; Quinn Konopacky 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2019
卷号：157
期号：3
页码：1-16
DOI：10.3847/1538-3881/aafb09
语种：English
出版社：American Institute of Physics
摘要：The Orion Nebula Cluster (ONC) is the nearest site of ongoing massive star formation, which allows us to study the kinematics and dynamics of the region in detail and constrain star formation theories. Using HST ACS/WFPC2/WFC3IR and Keck II NIRC2 data, we have measured the proper motions of 701 stars within an ∼6′×6′ field of view around the center of the ONC. We have found more than 10 escaping star candidates, concentrated predominantly at the core of the cluster. The proper motions of the bound stars are consistent with a normal distribution, albeit elongated north–south along the Orion filament, with proper-motion dispersions of * s s = m a m d ( ) ( ) , 0.83 0.02, 1.12 0.03 , masyr −1 or intrinsic velocity dispersions of * s s = a d ( ) ( ) , 1.57 0.04, 2.12 0.06 v v , , kms −1 assuming a distance of 400pc to the ONC. The cluster shows no evidence for tangential-to-radial anisotropy. Our velocity dispersion profile agrees with the prediction from the observed stellar + gas density profile from Da Rio et al., indicating that the ONC is in virial equilibrium. This finding suggests that the cluster was formed with a low star formation efficiency per dynamical timescale based on comparisons with current star formation theories. Our survey also recovered high-velocity IR sources BN, x and n in the BN/KL region. The estimated location of the first two sources ∼500yr ago agrees with that of the radio source I, consistent with their proposed common origin from a multistellar disintegration. However, source n appears to have a small proper motion and is unlikely to have been involved in the event.
关键词：open clusters and associations: individual (Orion Nebula Cluster);proper motions;stars: formation;stars: kinematics and dynamics