Fossil Imprints of the First-Generation Supernova Ejecta in Extremely Metal-deficient Stars
Fossil Imprints of the First-Generation Supernova Ejecta in Extremely Metal-deficient Stars
复制标题
DOI：
10.1086/311699
复制
发表时间：
1998-09
期刊：
影响因子：
--
通讯作者：
T. Shigeyama;T. Tsujimoto
中科院分区：
文献类型：
--
作者：
T. Shigeyama;T. Tsujimoto
利用核合成计算的结果与不同的祖先质量的理论核心坍缩超新星模型，它表明，C，Mg，Si，Ca，和H的丰度模式中看到的极端缺乏金属的恒星与[Fe/H]<$-2.5遵循在个人的第一代超新星遗迹（SNRs）中看到的。这表明大多数[Fe/H]= 2.5的恒星都是由单个超新星（SN）事件形成的。为了获得重元素与氢的比值，推导了在原始丰度的星际物质中，信噪比扫过的氢质量的估算公式。我们用[Mg/H]代替[Fe/H]来表示金属丰度。从这些SNRs预测的金属丰度[Mg/H]的范围从~-4到~-1.5，并且SN中Mg的质量与其祖先质量有很好的相关性。因此，在极度缺金属的星星中观察到的[Mg/H]与其前身质量有对应关系。较大的[Mg/H]对应于较大的祖细胞质量。因此，所谓的“年龄-金属丰度关系”对于[Fe/H]=-2.5的恒星并不成立。与此相反，[Mg/Fe]比的理论信噪比有一个不同的趋势，从那些极端缺乏金属的恒星。它还表明，从观察到的趋势[Mg/Fe]，人们可以预测每个SN的铁产量给出的对应关系[Mg/H]的祖质量。由此获得的Fe产率与SN光变曲线分析的结果一致。这表明在核心坍缩超新星爆炸或质量削减开始时建模仍然存在问题。在极端缺乏金属的恒星中，O的丰度测定，这还没有从观测分析中完成，是强烈需要的，以检验的假设，即在一个极端缺乏金属的星星中的元素来自一个单一的SN事件，并获得可靠的SNe产量。
Using the results of nucleosynthesis calculations for theoretical core-collapse supernova models with various progenitor masses, it is shown that the abundance patterns of C, Mg, Si, Ca, and H that are seen in extremely metal-deficient stars with [Fe/H]≲-2.5 follow those seen in the individual first-generation supernova remnants (SNRs). This suggests that most of the stars with [Fe/H]≲-2.5 were made from individual supernova (SN) events. To obtain the ratio of heavy elements to hydrogen, a formula is derived to estimate the mass of hydrogen swept up by an SNR when it occurs in the interstellar matter with the primordial abundances. We use [Mg/H] to indicate the metallicities instead of [Fe/H]. The metallicities [Mg/H] predicted from these SNRs range from ~-4 to ~-1.5, and the mass of Mg in an SN is well correlated with its progenitor mass. Thus, the observed [Mg/H] in an extremely metal-deficient star has a correspondence to the progenitor mass. A larger [Mg/H] corresponds to a larger progenitor mass. Therefore, the so-called "age-metallicity relation" does not hold for stars with [Fe/H]≲-2.5. In contrast, the [Mg/Fe] ratios in the theoretical SNRs have a different trend from those in extremely metal-deficient stars. It is also shown that from the observed trend of [Mg/Fe], one can predict the Fe yield of each SN given the correspondence of [Mg/H] to the progenitor mass. The Fe yields thus obtained are consistent with those derived from SN light-curve analyses. This indicates that there is still a problem in modeling a core-collapse supernova at the beginning of its explosion or mass cut. The abundance determination of O in extremely metal-deficient stars, which has not been done from observational analyses, is strongly desired in order to test the hypothesis that the elements in an extremely metal-deficient star come from a single SN event and to obtain reliable yields for SNe.