arXiv 0811.00202008-11astro-ph

银河系中可观测到的最小恒星金属丰度

The minimum stellar metallicity observable in the Galaxy

Anna Frebel, Jarrett L. Johnson, Volker Bromm

备注：: 5 pages, accepted for publication in MNRAS
DOI：: 10.1111/j.1745-3933.2008.00587.x

摘要：

第一批恒星通过产生高能辐射和第一批重化学元素，从根本上改变了早期宇宙。对宇宙演化的影响敏感地取决于它们的初始质量函数（IMF），这可以通过对我们银河系中古老的贫金属晕星的详细研究来进行经验约束。我们比较了最低的镁和铁丰度测量星系晕恒星的理论预测的最低恒星富集人口III恒星的假设下，头重脚轻的IMF。为了证明在贫金属恒星中测量的丰度反映了它们形成时的化学条件，因此它们可以用来推导对原始IMF的约束，我们对SDSS调查中的大样本贫金属恒星进行了详细的运动学分析。我们评估星际吸积是否改变了它们的表面丰度。我们发现，吸积一般是可以忽略不计的，即使在极低的水平，原始IMF可以测试。我们的结论是，大多数第一颗恒星都非常大，但质量可能低于140 M。

英文摘要：

The first stars fundamentally transformed the early Universe through their production of energetic radiation and the first heavy chemical elements. The impact on cosmic evolution sensitively depends on their initial mass function (IMF), which can be empirically constrained through detailed studies of ancient, metal-poor halo stars in our Galaxy. We compare the lowest magnesium and iron abundances measured in Galactic halo stars with theoretical predictions for the minimum stellar enrichment provided by Population III stars under the assumption of a top-heavy IMF. To demonstrate that abundances measured in metal-poor stars reflect the chemical conditions at their formation, and that they can thus be used to derive constraints on the primordial IMF, we carry out a detailed kinematic analysis of a large sample of metal-poor stars drawn from the SDSS survey. We assess whether interstellar accretion has altered their surface abundances. We find that accretion is generally negligible, even at the extremely low levels where the primordial IMF can be tested. We conclude that the majority of the first stars were very massive, but had likely masses below ~140 M.

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