通过外部反馈去除分子云包层会影响恒星形成的效率吗？
Can the removal of molecular cloud envelopes by external feedback affect the efficiency of star formation?
摘要：
我们研究如何恒星形成效率可以显着降低分子云的信封从外部来源的反馈删除。来自恒星形成的反馈很难阻止致密气体中的过程，但可以很容易地去除不发生恒星形成的密度较低和较温暖的包层。然而，包层可以发挥重要作用，通过加深引力势和提供约束压力边界来保持其宿主云的束缚。我们使用数值模拟表明，在所有情况下，在恒星形成效率（SFE）下降的云信封的结果。在1.38次自由落体时，我们的4 pc云模拟的SFE从16%下降到6%，而我们的5 pc云从27%下降到16%。同时，当信封丢失时，我们的3 pc云（最小约束）的SFE从5.67%下降到零。根据$α$，每自由落体时间的恒星形成效率从0到$\approx$ 0.25不等，$α$定义为动能加热能与引力能的比值，与恒星形成的绝对质量无关。此外，发现与包络损失相关的SFE下降甚至发生在稍后的时间。我们的结论是，SFE总是会下降，如果一个恒星形成的云失去了它的信封，由于恒星的反馈，与较少的约束云遭受最大的减少。
英文摘要：
We investigate how star formation efficiency can be significantly decreased by the removal of a molecular cloud's envelope by feedback from an external source. Feedback from star formation has difficulties halting the process in dense gas but can easily remove the less dense and warmer envelopes where star formation does not occur. However, the envelopes can play an important role keeping their host clouds bound by deepening the gravitational potential and providing a constraining pressure boundary. We use numerical simulations to show that removal of the cloud envelopes results in all cases in a fall in the star formation efficiency (SFE). At 1.38 free-fall times our 4 pc cloud simulation experienced a drop in the SFE from 16 to six percent, while our 5 pc cloud fell from 27 to 16 per cent. At the same time, our 3 pc cloud (the least bound) fell from an SFE of 5.67 per cent to zero when the envelope was lost. The star formation efficiency per free-fall time varied from zero to $\approx$ 0.25 according to $α$, defined to be the ratio of the kinetic plus thermal to gravitational energy, and irrespective of the absolute star forming mass available. Furthermore the fall in SFE associated with the loss of the envelope is found to even occur at later times. We conclude that the SFE will always fall should a star forming cloud lose its envelope due to stellar feedback, with less bound clouds suffering the greatest decrease.
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