Stellar Proper Motions in the Orion Nebula Cluster
Stellar Proper Motions in the Orion Nebula Cluster
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DOI：
10.3847/1538-3881/aafb09
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发表时间：
2018-12
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影响因子：
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通讯作者：
Dongwon Kim;Jessica R. Lu;Q. Konopacky;L. Chu;Elizabeth Toller;Jay Anderson;C. Theissen;M. Morris-M.-M
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文献类型：
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作者：
Dongwon Kim;Jessica R. Lu;Q. Konopacky;L. Chu;Elizabeth Toller;Jay Anderson;C. Theissen;M. Morris-M.-M
猎户座星云团（ONC）是离我们最近的正在形成的大质量星星的地方，这使我们能够详细研究该区域的运动学和动力学，并限制星星形成理论。利用HST ACS/WFPC 2/WFC 3 IR和Keck II NIRC 2观测数据，我们测量了701颗恒星绕ONC中心的自行。我们已经发现了10多颗逃逸的星星候选者，主要集中在星团的核心。束缚星的自行符合正态分布，尽管沿着猎户座暗条南北沿着拉长，自行色散为masyr −1或内禀速度色散为km s−1（假设到ONC的距离为400 pc）。该集群没有表现出切向径向各向异性的证据。我们的速度色散曲线与Da Rio等人从观测到的恒星+气体密度曲线预测的结果一致，表明ONC处于维里平衡。这一发现表明，根据与当前星星形成理论的比较，该星系团的形成在每个动力学时间尺度上的星星形成效率较低。我们的调查还恢复了BN/KL地区的高速红外源BN，x和n。前两个源的估计位置在1500年前与射电源I的位置一致，这与它们共同起源于多恒星解体的假设一致。然而，震源n似乎有一个小的自行，不太可能参与了该事件。
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 mas yr−1 or intrinsic velocity dispersions of km s−1 assuming a distance of 400 pc 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 ∼500 yr 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.