Inefficient star formation through turbulence, magnetic fields and feedback
Inefficient star formation through turbulence, magnetic fields and feedback
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通过湍流、磁场和反馈形成低效的恒星形成
DOI：
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
C. Federrath
中科院分区：
文献类型：
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作者：
C. Federrath
星星的形成是低效的。分子云中只有百分之几的可用气体形成恒星，导致观察到的低星星形成率（SFR）。当对许多分子云进行平均时，情况也是如此，因此整个星系的SFR又一次低得令人惊讶。事实上，考虑到低温，分子云应该是高度引力不稳定的，并在其全球平均自由落体时间尺度上崩溃。然而，据观察，它们的寿命延长了10-100倍，即，每自由落体时间SFR（SFR_ff）仅为百分之几。因此，其他物理机制必须抵消快速的全球崩溃。湍流，磁场和恒星反馈被认为是调节剂，但仍然不清楚这些过程中哪一个是最重要的，以及它们的相对贡献是什么。在这里，我们运行高分辨率的模拟，包括重力，湍流，磁场和射流/流出反馈。我们证实，云崩溃的平均自由落体时间，如果只考虑重力，生产恒星在一个不切实际的速度。相比之下，如果湍流、磁场和反馈被逐步地包括在内，则SFR随着每一个附加物理成分而减小2-3倍。当它们都一致行动时，我们发现一个常数SFR_ff = 0.04，目前与观测结果最接近，但仍然比平均值高出2-4倍。与其他模拟和观测的详细比较使我们得出结论，只有模型与湍流产生大维里参数，并包括磁场和反馈可以产生现实的SFR。
Star formation is inefficient. Only a few percent of the available gas in molecular clouds forms stars, leading to the observed low star formation rate (SFR). The same holds when averaged over many molecular clouds, such that the SFR of whole galaxies is again surprisingly low. Indeed, considering the low temperatures, molecular clouds should be highly gravitationally unstable and collapse on their global mean freefall timescale. And yet, they are observed to live about 10-100 times longer, i.e., the SFR per freefall time (SFR_ff) is only a few percent. Thus, other physical mechanisms must counteract the quick global collapse. Turbulence, magnetic fields and stellar feedback have been proposed as regulating agents, but it is still unclear which of these processes is the most important and what their relative contributions are. Here we run high-resolution simulations including gravity, turbulence, magnetic fields, and jet/outflow feedback. We confirm that clouds collapse on a mean freefall time, if only gravity is considered, producing stars at an unrealistic rate. In contrast, if turbulence, magnetic fields, and feedback are included step-by-step, the SFR is reduced by a factor of 2-3 with each additional physical ingredient. When they all act in concert, we find a constant SFR_ff = 0.04, currently the closest match to observations, but still about a factor of 2-4 higher than the average. A detailed comparison with other simulations and with observations leads us to conclude that only models with turbulence producing large virial parameters, and including magnetic fields and feedback can produce realistic SFRs.
DOI：
10.1088/2041-8205/721/2/l134
发表时间：
2010
期刊：
The Astrophysical Journal Letters
影响因子：
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作者：
Sharanya Sur;Dominik R. G. Schleicher;Robi Banerjee;Christoph Federrath;Ralf S. Klessen
通讯作者：
Ralf S. Klessen
自重力气体 (M)HD 模拟的新 Jean 分辨率准则：在重力驱动湍流磁场放大中的应用
DOI：
10.1088/0004-637x/731/1/62
发表时间：
2011
期刊：
The Astrophysical Journal
影响因子：
--
作者：
Christoph Federrath;Sharanya Sur;Dominik R. G Schleicher;Robi Banerjee;Ralf S. Klessen
通讯作者：
Ralf S. Klessen