The Kinematics of the Scorpius-Centaurus OB Association from Gaia DR1
The Kinematics of the Scorpius-Centaurus OB Association from Gaia DR1
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盖亚 DR1 中天蝎座-半人马座 OB 关联的运动学
DOI：
10.1093/mnras/sty207
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发表时间：
2018
影响因子：
4.8
通讯作者：
E. Mamajek
中科院分区：
文献类型：
--
作者：
N. Wright;E. Mamajek
我们使用盖亚 DR1 视差和自行对天蝎座-半人马座 (Sco-Cen) OB 关联 (Sco OB2) 进行运动学研究。我们的目标是检验经典理论，即 OB 星团是被残余气体排出等过程破坏的致密致密星团的扩展残余物。该协会 433 名成员中的 258 名成员可以使用盖亚天体测量法，其余成员则使用修订后的依巴谷天体测量法。我们使用这些数据来确认 Sco-Cen 的三个子群不受重力束缚，并且具有非各向同性的速度色散，这表明它们没有时间动态松弛。我们还探索了子群的内部运动学，以寻找扩张的证据。我们测试 Blaauw 的经典线性膨胀模型，搜索沿银轴的速度趋势，比较膨胀和非膨胀收敛点，假设线性轨迹并使用本轮近似进行回溯分析，并评估修正虚拟膨胀/收缩的自行膨胀的证据。这些方法都没有为子群的扩展提供一致的证据，也没有证据表明子群过去具有更紧凑的配置。我们发现了子群内运动子结构的证据，支持这样的观点，即它们不是由单个星团的破坏形成的。我们得出的结论是，Sco-Cen 很可能天生就是高度亚结构的，多个小规模的恒星形成事件对整个 OB 关联做出了贡献，而不是作为单个、整体的簇状恒星形成爆发。
We present a kinematic study of the Scorpius-Centaurus (Sco-Cen) OB association (Sco OB2) using Gaia DR1 parallaxes and proper motions. Our goal is to test the classical theory that OB associations are the expanded remnants of dense and compact star clusters disrupted by processes such as residual gas expulsion. Gaia astrometry is available for 258 out of 433 members of the association, with revised Hipparcos astrometry used for the remainder. We use this data to confirm that the three subgroups of Sco-Cen are gravitationally unbound and have non-isotropic velocity dispersions, suggesting they have not had time to dynamically relax. We also explore the internal kinematics of the subgroups to search for evidence of expansion. We test Blaauw's classical linear model of expansion, search for velocity trends along the Galactic axes, compare the expanding and non-expanding convergence points, perform traceback analysis assuming both linear trajectories and using an epicycle approximation, and assess the evidence for expansion in proper motions corrected for virtual expansion / contraction. None of these methods provide coherent evidence for expansion of the subgroups, with no evidence to suggest that the subgroups had a more compact configuration in the past. We find evidence for kinematic substructure within the subgroups that supports the view that they were not formed by the disruption of individual star clusters. We conclude that Sco-Cen was likely born highly substructured, with multiple small-scale star formation events contributing to the overall OB association, and not as single, monolithic bursts of clustered star formation.