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arXiv 0803.4053astro-ph
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恒星形成效率及其与初始质量函数变化的关系

The star formation efficiency and its relation to variations in the initial mass function

Paul C. Clark, Ian A. Bonnell, Ralf S. Klessen

摘要:

我们调查的动力学状态的支持,1000太阳质量,分子云的影响它形成的集群的属性,我们的讨论集中在恒星形成效率(SFE)和初始质量函数(IMF)。本文研究了各种初始能态,从PE = 0.1 KE的云到PE = 10 KE的云,以及等温和分段多方状态方程(类似于Larson提出的)。据发现,任意的恒星形成效率是可能的,与强烈的未绑定的云产生非常低的恒星形成效率。我们认为,在Maddelena云的低恒星形成效率可能是其内部结构的相对非束缚状态的后果。当云具有PE >= KE的初始能态时,竞争吸积导致了观测到的IMF。我们表明,在这样的条件下,IMF的形状是独立于时间的计算。这表明,全球吸积过程可以终止在任何阶段的集群的演变,而仍然产生的恒星质量分布是一致的,与观察到的IMF。当星云逐渐变得更加不受束缚时,竞争性吸积就不那么重要了,原恒星的质量函数也就变小了。这些结果预测,分子云应该充满了分布的恒星人口,遵循比Salpeter IMF更平坦的轨道。

英文摘要:

We investigate how the dynamical state of a turbulently supported, 1000 solar mass, molecular cloud affects the properties of the cluster it forms, focusing our discussion on the star formation efficiency (SFE) and the initial mass function (IMF). A variety of initial energy states are examined in this paper, ranging from clouds with PE = 0.1 KE to clouds with PE = 10 KE, and for both isothermal and piece-wise polytropic equations of state (similar to that suggested by Larson). It is found that arbitrary star formation efficiencies are possible, with strongly unbound clouds yielding very low star formation efficiencies. We suggest that the low star formation efficiency in the Maddelena cloud may be a consequence of the relatively unbound state of its internal structure. It is also found that competitive accretion results in the observed IMF when the clouds have initial energy states of PE >= KE. We show that under such conditions the shape of the IMF is independent of time in the calculations. This demonstrates that the global accretion process can be terminated at any stage in the cluster's evolution, while still yielding a distribution of stellar masses that is consistent with the observed IMF. As the clouds become progressively more unbound, competitive accretion is less important and the protostellar mass function flattens. These results predict that molecular clouds should be permeated with a distributed population of stars that follow a flatter than Salpeter IMF.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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