Implications of a non-universal IMF from C, N, and O abundances in very metal-poor Galactic stars and damped Lyαabsorbers
Implications of a non-universal IMF from C, N, and O abundances in very metal-poor Galactic stars and damped Lyαabsorbers
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来自金属贫乏的银河恒星和阻尼 Lyα 吸收体中 C、N 和 O 丰度的非通用 IMF 的影响
DOI：
10.1051/0004-6361/201016210
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发表时间：
2011
影响因子：
6.5
通讯作者：
K.
中科院分区：
文献类型：
--
作者：
Tsujimoto;T. and Bekki;K.
最近发现的在最缺乏金属的阻尼Lyα(DLA)吸收体中的C， N和O丰度与银河系晕中极度缺乏金属的恒星以及河外H II区域的丰度进行了比较，以破译早期宇宙的核合成和化学富集。这些比较令人惊讶地确定了相对较高的C/O比率和低N/O比率在DLA系统，这是难以解释的理论。我们提出，如果这些特征被未来的研究证实，这种效应的发生是因为贫金属DLA系统的初始质量函数在20-25M⊙左右的质量端有一个截止点，因此缺乏提供核合成产物的大质量恒星，导致低C/O和高N/O比率。这一发现合理地解释了DLA系统的性质，在DLA系统中，由于大质量恒星对电离的抑制，有足够数量的冷氢气体保持完整。此外，我们的声明有力地支持了非常大质量恒星的高N生成率，这可能是可以接受的，考虑到最近的核合成计算与快速旋转模型。丰度数据和核合成结果的更新将加强我们的新命题，即C/O和N/O丰度是推断初始质量函数形式的有力工具。
Recently revealed C, N, and O abundances in the most metal-poor damped Lyα(DLA) absorbers are compared with those of extremely metal-poor stars in the Galactic halo, as well as extragalactic H II regions, to decipher nucleosynthesis and chemical enrichment in the early Universe. These comparisons surprisingly identify a relatively high C/O ratio and a low N/O ratio in DLA systems, which is hard to explain theoretically. We propose that if these features are confirmed by future studies, this effect occurs because the initial mass function in metal-poor DLA systems has a cut-off at the upper mass end at around 20–25M⊙, thus lacks the massive stars that provide the nucleosynthesis products leading to the low C/O and high N/O ratios. This finding is a reasonable explanation of the nature of DLA systems in which a sufficient amount of cold H I gas remains intact because of the suppression of ionization by massive stars. In addition, our claim strongly supports a high production rate of N in very massive stars, which might be acceptable in light of the recent nucleosynthesis calculations with fast rotation models. The updates of both abundance data and nucleosynthesis results will strengthen our novel proposition that the C/O and N/O abundances are a powerful tool for inferring the form of the initial mass function.