The Initial Mass Function
The Initial Mass Function
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DOI：
10.1007/978-94-009-2973-9_42
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发表时间：
1988
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影响因子：
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通讯作者：
R. Larson
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文献类型：
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作者：
R. Larson
正如我们已经听说的那样，对恒星形成云中转化为恒星的比例以及星系中总体恒星形成率的估计在很大程度上取决于假设的恒星初始质量函数，在得出有关星系演化的任何定量结论之前必须先知道该函数。此时强调仍然存在的巨大不确定性可能更有用，而不是试图总结有关该主题的当前知识。 Walterbos 在关于 M31 恒星形成的精彩演讲中明确了这些不确定性的重要性：为了从表明存在大质量恒星数量的各种数据得出总恒星形成率，Walterbos 采用了 Kennicutt 之前使用的“中间路线”IMF，但指出如果改用 Miller 和 Scalo 在 1979 年提出的更陡峭的 IMF，则推断的恒星形成率必须乘以3.4，而如果采用 x = 1 的更平坦的 IMF（参见 Van Buren, Astrophys. J. 294, 567, 1985），则 SFR 将乘以 0.25。因此，Walterbos 采用的折衷 IMF 可能会产生四倍不正确的 SFR，而且我们甚至不确定它是否更有可能过高或过低。尽管如此，应该指出的是，范布伦最近的工作比以前的研究使用了更大的恒星样本，并对灭绝进行了更仔细的校正，结果是更平坦的IMF，即更大比例的大质量恒星。这表明广泛使用的 Miller-Scalo IMF 对于最大质量的恒星来说可能过于陡峭，并且许多基于它的估计恒星形成率应该向下修正。
As we have already heard, estimates of the fraction of a star-forming cloud that is converted into stars and of the overall star formation rate in galaxies depend crucially on the assumed stellar initial mass function, which must be known before any quantitative conclusions can be drawn about galactic evolution. Instead of attempting to summarize current knowledge on the subject, it may be more useful at this point to emphasize the large uncertainties that still remain. The importance of these uncertainties was made clear in the excellent talk by Walterbos on star formation in M31: in order to derive the total star formation rate from various data indicating the number of massive stars present, Walterbos adopted a “middle-of-the-road” IMF previously used by Kennicutt, but pointed out that if the steeper IMF proposed by Miller and Scalo in 1979 were used instead, the inferred SFR would have to be multiplied by 3.4, whereas if a flatter IMF withx =1 (cf. Van Buren,Astrophys. J. 294, 567, 1985) were adopted, the SFR would be multiplied by 0.25. Thus the compromise IMF adopted by Walterbos could yield an SFR that is incorrect by a factor of four, and we are not even sure whether it is more likely to be too high or too low. It should nevertheless be noted that Van Buren’s more recent work used a larger sample of stars than previous studies and applied more careful corrections for extinction, and the result was a flatter IMF, i.e. a larger proportion of massive stars. This suggests that the widely used Miller-Scalo IMF may be too steep for the most massive stars, and that many estimated SFRs based on it should be revised downward.