Origins of carbon-enhanced metal-poor stars
Origins of carbon-enhanced metal-poor stars
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DOI：
10.1093/mnras/stx2392
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发表时间：
2016-11
影响因子：
4.8
通讯作者：
M. Sharma;T. Theuns;C. Frenk;R. Cooke
中科院分区：
文献类型：
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作者：
M. Sharma;T. Theuns;C. Frenk;R. Cooke
我们研究了从Eagle宇宙流体力学模拟中选取的银河系(MW)中碳增强型贫金属星(CEMP)的性质。EAGLE中的恒星演化模型包括由渐近巨星分支(AGB)恒星、来自大质量恒星的风以及Ia型和II型超新星(SNE)丰富的物理。在模拟中，由于有效的恒星反馈，年轻的MW前体恒星的形成是爆发的，这使得不良的金属混合导致形成具有极端丰度模式的CEMP恒星。出现了两类CEMP恒星：一类主要由低金属丰度的II型SNE富集，低铁产量驱动银河系外流；另一类主要由AGB恒星富集，当一个贫气星系吸积原始气体时。第一类类似于CEMP-NO星，具有高[C/Fe]和低[C/O]，第二类类似于CEMP-S星，其元素丰富且[C/O]值高。这两个富集通道解释了数据中看到的几个趋势：(I)低[O/H]和降低[O/H]时[C/O]的散射度和中位数的增加，(Ii)[Fe/H]或[C/H]非常低的恒星的趋势是CEMP-NO型，以及(Iii)贫金属星中原子序数的[α/Fe]的散布减少。在这种解释中，Cemp-no恒星得到了恒星的丰富，这些恒星使星系能够重新电离宇宙。
We investigate the nature of carbon-enhanced metal-poor (CEMP) stars in Milky Way (MW) analogues selected from the EAGLE cosmological hydrodynamical simulation. The stellar evolution model in EAGLE includes the physics of enrichment by asymptotic giant branch (AGB) stars, winds from massive stars, and Type Ia and Type II supernovae (SNe). In the simulation, star formation in young MW progenitors is bursty due to efficient stellar feedback, which enables poor metal mixing leading to the formation of CEMP stars with extreme abundance patterns. Two classes of CEMP stars emerge: those mostly enriched by low-metallicity Type II SNe with low Fe yields that drive galactic outflows, and those mostly enriched by AGB stars when a gas-poor galaxy accretes pristine gas. The first class resembles CEMP-no stars with high [C/Fe] and low [C/O], the second class resembles CEMP-s stars overabundant in s-process elements and high values of [C/O]. These two enrichment channels explain several trends seen in data: (i) the increase in the scatter and median of [C/O] at low and decreasing [O/H], (ii) the trend of stars with very low [Fe/H] or [C/H] to be of type CEMP-no and (iii) the reduction in the scatter of [α/Fe] with atomic number in metal-poor stars. In this interpretation, CEMP-no stars were enriched by the stars that enabled galaxies to reionize the Universe.