The 3D Kinematics of the Orion Nebula Cluster: NIRSPEC-AO Radial Velocities of the Core Population
The 3D Kinematics of the Orion Nebula Cluster: NIRSPEC-AO Radial Velocities of the Core Population
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DOI：
10.3847/1538-4357/ac3252
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发表时间：
2021-05
期刊：
影响因子：
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通讯作者：
C. Theissen;Q. Konopacky;Jessica R. Lu;Dongwon Kim;S. Y. Zhang;C. Hsu;L. Chu;Lingfeng Wei
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文献类型：
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作者：
C. Theissen;Q. Konopacky;Jessica R. Lu;Dongwon Kim;S. Y. Zhang;C. Hsu;L. Chu;Lingfeng Wei
年轻的、仍在形成的星系团内恒星和星下群体的运动学和动力学为约束形成机制的理论提供了有价值的信息。利用Keck II NIRSpec+AO数据，我们测量了猎户座星系团(ONC)核心4‘范围内56个低质量源的径向速度。我们还重新测量了用SDSS/APOEE观测到的172个震源的径向速度。这些数据与使用HST ACS/WFPC2/WFC3IR和Keck II NIRC2测量的自行相结合，创建了具有所有三个速度分量的135个震源的样本。测得的速度在所有三个分量上都符合正态分布。我们测量了(σvα，σvδ，σVr)=(1.6 4±0.12，2.0 3±0.13，2.5 6−0.17+0.16)KM S−1的本征速度弥散。我们计算的本征速度弥散分布与Da Rio等人的动力学平衡模型一致。(2014)在切向而不是在视线方向，这可能表明ONC的核心还没有维格化，可能需要一个非球面的势来解释观测到的速度弥散分布。我们还观察到在细丝之后沿南北方向的轻微伸长，这在以前的文献中已经被很好地研究过，并且在视线到切向速度方向上也有伸长。这些3D运动学将有助于开发真实的大质量星系团形成和早期演化模型。
The kinematics and dynamics of stellar and substellar populations within young, still-forming clusters provide valuable information for constraining theories of formation mechanisms. Using Keck II NIRSPEC+AO data, we have measured radial velocities for 56 low-mass sources within 4′ of the core of the Orion Nebula Cluster (ONC). We also remeasure radial velocities for 172 sources observed with SDSS/APOGEE. These data are combined with proper motions measured using HST ACS/WFPC2/WFC3IR and Keck II NIRC2, creating a sample of 135 sources with all three velocity components. The velocities measured are consistent with a normal distribution in all three components. We measure intrinsic velocity dispersions of ( σvα , σvδ , σvr ) = (1.64 ± 0.12, 2.03 ± 0.13, 2.56−0.17+0.16 ) km s−1. Our computed intrinsic velocity dispersion profiles are consistent with the dynamical equilibrium models from Da Rio et al. (2014) in the tangential direction but not in the line-of-sight direction, possibly indicating that the core of the ONC is not yet virialized, and may require a nonspherical potential to explain the observed velocity dispersion profiles. We also observe a slight elongation along the north–south direction following the filament, which has been well studied in previous literature, and an elongation in the line-of-sight to tangential velocity direction. These 3D kinematics will help in the development of realistic models of the formation and early evolution of massive clusters.