Seeding the second star – II. CEMP star formation enriched from faint supernovae
Seeding the second star – II. CEMP star formation enriched from faint supernovae
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DOI：
10.1093/mnras/staa2144
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发表时间：
2020-07
影响因子：
4.8
通讯作者：
G. Chiaki;J. Wise;S. Marassi;R. Schneider;M. Limongi;A. Chieffi
中科院分区：
文献类型：
--
作者：
G. Chiaki;J. Wise;S. Marassi;R. Schneider;M. Limongi;A. Chieffi
碳增强贫金属（CEMP）恒星是保存着早期恒星化学富集记录的活化石。在这项工作中，我们对第一代无金属（Pop III）恒星的超新星（SN）富集和富集云的引力坍缩进行了一组数值模拟，考虑了所有相关的冷却/加热过程和化学反应以及尘埃颗粒的生长。我们首次采用了具有原始质量的微弱SN模型 $M_{\rm PopIII} = 13$--$80 \ {\rm M}_{\bigodot}$，产生c增强丰度模式(${\rm [C/Fe]} = 4.57$--$4.75$)通过喷射物最内层的混合和回退。该模型还考虑了尘埃颗粒的形成和破坏。我们发现SN喷射出的金属可以部分被相同的暗物质微晕重新吸积，并且富集云的碳丰度 $A({\rm C}) = 3.80$--$5.06$ 低于观测到的CEMP恒星($A({\rm C}) \gtrsim 6$)，因为暗淡的SNe喷出的金属质量比正常的核心坍缩SNe要小，这是由于大面积的后撤。我们还发现云的破碎是由碳质颗粒的气体冷却引起的 $M_{\rm PopIII} = 13 \ {\rm M}_{\bigodot}$ 即使是铁含量最低的地方 ${\rm [Fe/H]} \sim -9$． 这导致了低质量恒星的形成，这些“千兆金属贫乏”的恒星可以存活到今天的宇宙，并可能在未来的观测中被发现。
Carbon-enhanced metal-poor (CEMP) stars are the living fossils holding records of chemical enrichment from early generations of stars. In this work, we perform a set of numerical simulations of the enrichment from a supernova (SN) of a first generation of metal-free (Pop III) star and the gravitational collapse of the enriched cloud, considering all relevant cooling/heating processes and chemical reactions as well as the growth of dust grains. We adopt faint SN models for the first time with progenitor masses $M_{\rm PopIII} = 13$--$80 \ {\rm M}_{\bigodot}$, which yield C-enhanced abundance patterns (${\rm [C/Fe]} = 4.57$--$4.75$) through mixing and fallback of innermost layers of the ejecta. This model also considers the formation and destruction of dust grains. We find that the metals ejected by the SN can be partly re-accreted by the same dark matter minihalo, and carbon abundance of the enriched cloud $A({\rm C}) = 3.80$--$5.06$ is lower than the abundance range of observed CEMP stars ($A({\rm C}) \gtrsim 6$) because the mass of the metals ejected by faint SNe is smaller than normal core-collapse SNe due to extensive fallback. We also find that cloud fragmentation is induced by gas cooling from carbonaceous grains for $M_{\rm PopIII} = 13 \ {\rm M}_{\bigodot}$ even with the lowest iron abundance ${\rm [Fe/H]} \sim -9$. This leads to the formation of low-mass stars, and these ``giga metal-poor'' stars can survive until the present-day Universe and may be found by future observations.