A Holistic Scenario of Turbulent Molecular Cloud Evolution and Control of the Star Formation Efficiency: First Tests
A Holistic Scenario of Turbulent Molecular Cloud Evolution and Control of the Star Formation Efficiency: First Tests
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湍流分子云演化和恒星形成效率控制的整体场景：首次测试
DOI：
10.1086/374325
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
R. Klessen
中科院分区：
文献类型：
--
作者：
E. Vázquez;J. Ballesteros;R. Klessen
我们编制了一个分子云演化和控制星星形成效率（SFE）的整体方案，并给出了第一组数值试验。一个有损耗的可压缩级联可以产生密度波动和进一步的湍流在小尺度上从大尺度运动，这意味着在分子云中的湍流可能起源于形成它们的压缩。低于音速尺度λs时，湍流不能引起任何进一步的亚碎裂，也不能成为对抗重力的主要支撑剂。由于逐渐变小的密度峰值包含逐渐变小的质量分数，我们预计SFE随着λs的减小而减小，至少当云被湍流整体支持时。我们的数值实验证实了这一预测。我们还发现，崩溃的质量分数在模拟总是饱和低于100%的效率。这可能是由于剩余的团间介质的平均密度降低，而在真实的云中（不限于盒子），团间介质应该更容易分散，标志着云的“死亡”。我们确定了SFE对λs的两种不同的函数依赖（“模式”），它们大致对应于全局支持和不支持的情况。在最大尺度上具有大部分湍流能量的全球支持运行与无支持运行具有类似的SFE，提供了湍流双重作用的数值证据，即湍流除了提供支持外，还通过其大尺度模式在较小尺度上诱导崩溃。我们初步认为，这些模式可能对应于集群和孤立的模式的星星形成，虽然在这里，他们被视为形成一个连续的一部分，而不是单独的模式。最后，我们比较了以前的建议，相关的参数是能量注入规模。
We compile a holistic scenario for molecular cloud (MC) evolution and control of the star formation efficiency (SFE) and present a first set of numerical tests of it. A lossy compressible cascade can generate density fluctuations and further turbulence at small scales from large-scale motions, implying that the turbulence in MCs may originate from the compressions that form them. Below a sonic scale λs, turbulence cannot induce any further subfragmentation nor can it be a dominant support agent against gravity. Since progressively smaller density peaks contain progressively smaller fractions of the mass, we expect the SFE to decrease with decreasing λs, at least when the cloud is globally supported by turbulence. Our numerical experiments confirm this prediction. We also find that the collapsed mass fraction in the simulations always saturates below 100% efficiency. This may be due to the decreased mean density of the leftover interclump medium, which in real clouds (not confined to a box) should then be more easily dispersed, marking the "death" of the cloud. We identify two different functional dependences ("modes") of the SFE on λs, which roughly correspond to globally supported and unsupported cases. Globally supported runs with most of the turbulent energy at the largest scales have similar SFEs to those of unsupported runs, providing numerical evidence of the dual role of turbulence, whereby turbulence, besides providing support, induces collapse at smaller scales through its large-scale modes. We tentatively suggest that these modes may correspond to the clustered and isolated modes of star formation, although here they are seen to form part of a continuum rather than being separate modes. Finally, we compare with previous proposals that the relevant parameter is the energy injection scale.