The dynamical state of stellar structure in star‐forming regions
The dynamical state of stellar structure in star‐forming regions
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恒星形成区恒星结构的动力学状态
DOI：
10.1111/j.1365-2966.2011.19748.x
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发表时间：
2011
影响因子：
4.8
通讯作者：
S. Andrews
中科院分区：
文献类型：
--
作者：
J. Kruijssen;T. Maschberger;N. Moeckel;C. Clarke;N. Bastian;Ian A. Bonnell Utrecht;Leiden;Mpa Garching;I. Cambridge;Bonn;Grenoble;Excellence Cluster Munich;S. Andrews
形成束缚星星团的星星的比例受到恒星形成的密度谱和恒星结构对气体排出的反应的影响。我们分析流体动力学模拟的恒星形成区域的湍流碎片，以评估由此产生的人口的恒星和（子）集群的动力学特性。恒星子集群使用最小生成树算法进行识别。当只考虑恒星的引力势而忽略气体时，我们发现所识别的子星系团接近维里平衡（典型的维里比Qvir = 0.59，而维里平衡为Qvir = 0.5）。 这种维里态是由于气体吸积到恒星上，以及吸积引起的子星系团收缩，导致子星系团内气体比例较低的结果。由于子星系团是气体贫乏的，在模拟结束时达到0.1-0.2 pc的长度尺度，它们只受到气体排出的微弱影响。子星系团达到高密度所需的演化到气体贫乏状态的比例随着恒星形成区域的密度而增加。我们将这一论点扩展到星星星团尺度，并建议，气体的缺乏表明，早期的星星星团的破坏，由于气体驱逐（婴儿死亡率）发挥的作用比预期的要小，并可能局限于低环境气体密度的恒星形成区域。我们认为，在致密的恒星形成区，周围气体云对年轻星星团的潮汐冲击可能是早期破坏的原因。 这种“残酷的摇篮效应”除了通过气体排出来破坏外，还会起作用。我们提出了可能的方法来量化这两种机制的相对贡献。
The fraction of star formation that results in bound star clusters is influenced by the density spectrum in which stars are formed and by the response of the stellar structure to gas expulsion. We analyse hydrodynamical simulations of turbulent fragmentation in star-forming regions to assess the dynamical properties of the resulting population of stars and (sub)clusters. Stellar subclusters are identified using a minimum spanning tree algorithm. When considering only the gravitational potential of the stars and ignoring the gas, we find that the identified subclusters are close to virial equilibrium (the typical virial ratio Qvir≈ 0.59, where virial equilibrium would be Qvir∼ 0.5). This virial state is a consequence of the low gas fractions within the subclusters, caused by the accretion of gas on to the stars and the accretion-induced shrinkage of the subclusters. Because the subclusters are gas poor, up to a length-scale of 0.1–0.2 pc at the end of the simulation, they are only weakly affected by gas expulsion. The fraction of subclusters that reaches the high density required to evolve to a gas-poor state increases with the density of the star-forming region. We extend this argument to star cluster scales, and suggest that the absence of gas indicates that the early disruption of star clusters due to gas expulsion (infant mortality) plays a smaller role than anticipated, and is potentially restricted to star-forming regions with low ambient gas densities. We propose that in dense star-forming regions, the tidal shocking of young star clusters by the surrounding gas clouds could be responsible for the early disruption. This ‘cruel cradle effect’ would work in addition to disruption by gas expulsion. We suggest possible methods to quantify the relative contributions of both mechanisms.
DOI：
10.1088/0067-0049/188/1/139
发表时间：
2010-04
期刊：
The Astrophysical Journal Supplement Series
影响因子：
--
作者：
R. Launhardt;D. Nutter;D. Ward-Thompson;T. Bourke;T. Henning;T. Khanzadyan;T. Khanzadyan;M. Schmalzl;S. Wolf;S. Wolf;R. Zylka
通讯作者：
R. Launhardt;D. Nutter;D. Ward-Thompson;T. Bourke;T. Henning;T. Khanzadyan;T. Khanzadyan;M. Schmalzl;S. Wolf;S. Wolf;R. Zylka