The Origin of the Most Iron-poor Star
The Origin of the Most Iron-poor Star
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最贫铁恒星的起源
DOI：
10.1088/0004-637x/794/2/100
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
N.
中科院分区：
文献类型：
--
作者：
Marassi;S.; Chiaki;G.; Schneider;R.; Limongi;M.; Omukai;K.; Nozawa;T.; Chieffi;A.; Yoshida;N.
我们从最近发现的[Fe/H]<；-7.1星SMSS J031300开始，研究了碳增强贫金属星(CEMP)的起源。我们发现，在SMSS J031300表面观察到的元素丰度可以很好地与微弱的、无金属的超新星(SNE)的产额相吻合。利用适当校准的弱SN爆炸模型，我们首次研究了这种富碳、贫铁的SN喷射物中尘埃颗粒的形成。计算采用了未混合和均匀混合的喷射物，并考虑了SN反向激波的部分破坏。我们发现，由于除碳之外难熔元素的缺乏，无定形碳是唯一形成的颗粒物种，碳凝结效率在(0.025.15~0.84)之间，导致粉尘产量在(0.025-2.2 5)M☉范围内。我们跟踪了由这些微弱的SN爆炸产物丰富的恒星形成云的崩塌和碎裂，并探索了细结构线冷却和尘埃冷却所起的作用。我们发现，即使在崩塌过程中的颗粒生长对尘气比的影响很小，但由于在崩塌的早期阶段C被耗尽成CO分子，诸如SMSS J031300这样的CEMP小质量恒星的形成可能被尘埃冷却和碎裂所触发。模型预测和对C正常和富C贫金属星样本的观测之间的比较支持这样一种观点，即第一批低质量恒星的形成可能是单一的共同路径造成的。
We investigate the origin of carbon-enhanced metal-poor (CEMP) stars starting from the recently discovered [Fe/H]<-7.1 star SMSS J031300. We show that the elemental abundances observed on the surface of SMSS J031300 can be well fit by the yields of faint, metal-free, supernovae (SNe). Using properly calibrated faint SN explosion models, we study, for the first time, the formation of dust grains in such carbon-rich, iron-poor SN ejecta. Calculations are performed assuming both unmixed and uniformly mixed ejecta and taking into account the partial destruction by the SN reverse shock. We find that, due to the paucity of refractory elements beside carbon, amorphous carbon is the only grain species to form, with carbon condensation efficiencies that range between (0.15 and 0.84), resulting in dust yields in the range (0.025–2.25) M☉. We follow the collapse and fragmentation of a star-forming cloud enriched by the products of these faint SN explosions and we explore the role played by fine structure line cooling and dust cooling. We show that even if grain growth during the collapse has a minor effect of the dust-to-gas ratio, due to C depletion into CO molecules at an early stage of the collapse, the formation of CEMP low-mass stars, such as SMSS J031300, could be triggered by dust cooling and fragmentation. A comparison between model predictions and observations of a sample of C-normal and C-rich metal-poor stars supports the idea that a single common pathway may be responsible for the formation of the first low-mass stars.