s- process enrichment of ultrafaint dwarf galaxies
s- process enrichment of ultrafaint dwarf galaxies
复制标题
超微弱矮星系的s过程富集
DOI：
10.1093/mnras/stab1487
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发表时间：
2021
影响因子：
4.8
通讯作者：
Frebel, Anna
中科院分区：
文献类型：
--
作者：
Tarumi, Yuta;Suda, Takuma;van de Voort, Freeke;Inoue, Shigeki;Yoshida, Naoki;Frebel, Anna
我们研究了超暗矮星(UFDs)中钡(BA)和锶(Sr)的产生。这两个过程都产生了这些元素，人们可以从特征过程丰度模式中推断出过程的贡献，而过程的贡献在很大程度上仍然是未知的。我们发现，来自渐近巨星分支(AGB)恒星的洋流过程产额不足以解释在UFD中观测到的Ba和Sr丰度。这些元素的产生需要从星系中恒星形成的开始就有效地进行。即使我们考虑超 恒星的过程，接近或超过1个AGBdex的差异也是不协调的。我们假设旋转大质量恒星(RMS)和电子捕获超新星(ECSNe)是额外的贡献者，从而考虑一种可能的解决方案。我们发现，如果∼10%的大质量恒星以300kM的S−1的速度旋转，则RMS可能是UFDs中Ba的来源。至于ECSNe，我们认为它们在核心塌缩超新星中所占比例不到2%。它将前驱质量范围缩小到−3≲[Fe/H]≲−2。我们还探索了另一种分辨率，通过修改UFD中的恒星初始质量函数，找到了一个重现观测到的Ba丰度的顶光初始质量函数模型。未来确定或严格限制Eu和N丰度的观测对于确定UFD中的Ba和Sr的来源至关重要。
We study the production of barium (Ba) and strontium (Sr) in ultrafaint dwarf (UFDs) galaxies. Bothr- ands- processes produce these elements, and one can infer the contribution of ther-process from the characteristicr-process abundance pattern, whereas thes-process contribution remains largely unknown. We show that the currents-process yield from asymptotic giant branch (AGB) stars is not sufficient to explain the Ba and Sr abundances observed in UFDs. Production of these elements would need to be efficient from the beginning of star formation in the galaxies. The discrepancy of nearly or more than 1 dex is not reconciled even if we considers-process in super-AGB stars. We consider a possible resolution by assuming rotating massive stars (RMSs) and electron-capture supernovae (ECSNe) as additional contributors. We find that the RMSs could be the origin of Ba in UFDs if ∼10 per cent of massive stars are rotating at 300 km s−1. As for ECSNe, we argue that their fraction is less than 2 per cent of core-collapse supernova. It narrows the progenitor mass-range toat −3 ≲ [Fe/H] ≲ −2. We also explore another resolution by modifying the stellar initial mass function (IMF) in UFDs and find a top-light IMF model that reproduces the observed level of Ba-enrichment. Future observations that determine or tightly constrain the europium and nitrogen abundances are crucial to identify the origin of Ba and Sr in UFDs.