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arXiv 0909.4304astro-ph.SR
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湍流流体动力学模拟中年轻星系团的恒星动力学

Stellar Kinematics of Young Clusters in Turbulent Hydrodynamic Simulations

S. S. R. Offner, C. E. Hansen, M. R. Krumholz

备注：
5 pages, 4 figures, accepted to ApJL
发表信息：
Astrophys.J.704:L124-L128,2009
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摘要：

新形成的星团的运动学是有趣的，既可以作为恒星形成的气体云状态的探测器，也因为它们影响行星形成、恒星质量分离、星团破裂和其他过程，这些过程部分由年轻星团中的动力学相互作用控制。然而，到目前为止，还没有人尝试使用模拟恒星团簇形成来研究年轻恒星的运动学是如何随着其母体分子云性质的变化而变化的。在这封信中，我们报告的结果湍流自引力模拟的团簇形成，我们认为这两个云维里平衡和那些经历全球崩溃。我们发现，在这些模拟中的恒星通常有速度色散小于气体的一个因素的~ 5，独立的母云的动力学状态，使subvirial恒星速度色散自然出现，即使在维里化分子云。模拟的星系团还显示了~0.2-2 km s $^{-1}$ pc $^{-1}$的大尺度恒星速度梯度以及恒星和气体质心速度之间的强相关性，这两者都是在年轻的星系团中观察到的。我们的结论是星团应该显示亚维里速度色散，大尺度的速度梯度，以及强大的气体-恒星速度的相关性，无论其母云是否维里平衡，相反，这些功能的观测不能用来推断母气体云的动力学状态。

英文摘要：

The kinematics of newly-formed star clusters are interesting both as a probe of the state of the gas clouds from which the stars form, and because they influence planet formation, stellar mass segregation, cluster disruption, and other processes controlled in part by dynamical interactions in young clusters. However, to date there have been no attempts to use simulations of star cluster formation to investigate how the kinematics of young stars change in response to variations in the properties of their parent molecular clouds. In this letter we report the results of turbulent self-gravitating simulations of cluster formation in which we consider both clouds in virial balance and those undergoing global collapse. We find that stars in these simulations generally have velocity dispersions smaller than that of the gas by a factor of ~ 5, independent of the dynamical state of the parent cloud, so that subvirial stellar velocity dispersions arise naturally even in virialized molecular clouds. The simulated clusters also show large-scale stellar velocity gradients of ~0.2-2 km s$^{-1}$ pc$^{-1}$ and strong correlations between the centroid velocities of stars and gas, both of which are observed in young clusters. We conclude that star clusters should display subvirial velocity dispersions, large-scale velocity gradients, and strong gas-star velocity correlations regardless of whether their parent clouds are in virial balance, and, conversely, that observations of these features cannot be used to infer the dynamical state of the parent gas clouds.

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