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Study on a formation and chemical evolution of the Galaxy based on spectroscopic observations of metal-poor stars

基于贫金属恒星光谱观测的星系形成和化学演化研究

基本信息

批准号：
13640246
负责人：
HIDAI Masahide
金额：
$ 1.98万
依托单位：
Tokai University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2004
项目状态：
已结题

项目摘要

1. Our spectroscopic studies of alpha- elements, O, Si, S, and Ca, in metal-poor stars were carried out to investigate their behaviors against metalicity [Fe/H]. As for O, the abundance derived from the triplet lines was found to show a flat trend. The behaviors of Si and Ca show a correlated trend and were found to be classified into three groups based on dynamical properties. As for S, our result of an increasing trend with decreasing [Fe/H] in a paper of 2002 was first derived from a large sample, and inspired other groups as well as us to make further studies of S behavior. Our result obtained in a paper of 2005 confirmed that S shows a flat trend in -4 <[Fe/H]<-1, which may be explained by chemical evolution models based on standard supernovae nucleosynthesis.2. Other light elements of Li, Na, and K were also studied and found to provide the new results being different from the previous ones.3. The behavior of Zinc in very metal-poor stars was found to show an increasing trend below [Fe/H]<-3, which gives an important constraints to supernova models.4. The behaviors of r-process elements were found to show a large star-to-star scatter and to be explained by r-process nucleosynthesis. However, an unknown process was needed for an explanation of behaviors of Sr and Ba.5. The most iron-deficient star was discovered. The star may be a population III, or even if not, it gives strong constraints to a nature of the first generation stars in the beginning of the Galaxy.

1. 我们对贫金属恒星中的α -元素O、Si、S和Ca进行了光谱研究，以研究它们对金属丰度[Fe/H]的影响。对于O，从三重系得到的丰度呈平缓趋势。Si和Ca的行为呈相关趋势，根据动力学性质可分为三类。对于S，我们在2002年的一篇论文中得出的[Fe/H]随减小而增加的结果，首先是从一个大样本中得出的，并启发了其他团队和我们进一步研究S的行为。我们在2005年的一篇论文中得到的结果证实，S在-4 <[Fe/H]<-1时呈平坦趋势，这可以用基于标准超新星核合成的化学进化模型来解释。对Li、Na、K等其他轻元素也进行了研究，得到了不同于以往的新结果。锌在非常缺金属的恒星中的行为在[Fe/H]<-3时呈增加趋势，这给超新星模型提供了一个重要的约束。发现r过程元素的行为表现出较大的星间散射，并可以用r过程核合成来解释。然而，需要一个未知的过程来解释Sr和Ba.5的行为。发现了最缺铁的恒星。这颗恒星可能是III星族，即使不是，它也强烈限制了银河系开始时第一代恒星的性质。