论文标题

原始的内部星系调查(PIGS)V:对银河系早期组装的化学研究,与凸起中最贫穷的恒星在

The Pristine Inner Galaxy Survey (PIGS) V: a chemo-dynamical investigation of the early assembly of the Milky Way with the most metal-poor stars in the bulge

论文作者

Sestito, Federico, Venn, Kim A., Arentsen, Anke, Aguado, David, Kielty, Collin L., Lardo, Carmela, Martin, Nicolas F., Navarro, Julio F., Starkenburg, Else, Waller, Fletcher, Carlberg, Raymond G., François, Patrick, Hernández, Jonay I. González, Kordopatis, Georges, Vitali, Sara, Yuan, Zhen

论文摘要

银河凸起中金属贫困尾巴的研究提供了有关早期银河系组装和进化的独特信息。基于双子座/graces光谱进行了对原始星系内的原始星系调查中选择的17个非常贫穷的恒星(VMP,[Fe/H] $ <-2.0 $)的化学分析。化学表明,我们的大多数恒星与银河光环中的金属贫困恒星非常相似。根据{\ it gaia} eDR3计算得出的轨道意味着这些恒星在最早的银河系组件中被带入凸起。我们的大多数恒星具有较大的[Na,ca/mg]丰度,因此几乎没有配对超新星富集的证据。我们的两个恒星(P171457,P184700)具有与第二代球状簇星兼容的化学丰度,这表明内部银河系中的古代和现在溶解的球状簇存在。其中之一(P171457)是极为贫困的([Fe/H] $ <-3.0 $),远低于球状簇的金属层地板,这支持了越来越多的早期宇宙中较低金属金属簇的证据。第三颗星(P180956,[Fe/h] $ \ sim-2 $)具有低[Na,ca/mg]和非常低的[ba/fe]的金属性,这与仅一个或几个低质量的超级novae污染的系统中的形成是一致的。有趣的是,它的轨道局限于银河平面,就像文献中发现的其他非常贫穷的恒星一样,与银河系中最早的构建块有关。

The investigation of the metal-poor tail in the Galactic bulge provides unique information on the early Milky Way assembly and evolution. A chemo-dynamical analysis of 17 very metal-poor stars (VMP, [Fe/H] $<-2.0$) selected from the Pristine Inner Galaxy Survey was carried out based on Gemini/GRACES spectra. The chemistry suggests that the majority of our stars are very similar to metal-poor stars in the Galactic halo. Orbits calculated from {\it Gaia} EDR3 imply these stars are brought into the bulge during the earliest Galactic assembly. Most of our stars have large [Na,Ca/Mg] abundances, and thus show little evidence of enrichment by pair-instability supernovae. Two of our stars (P171457, P184700) have chemical abundances compatible with second-generation globular cluster stars, suggestive of the presence of ancient and now dissolved globular clusters in the inner Galaxy. One of them (P171457) is extremely metal-poor ([Fe/H] $<-3.0$) and well below the metallicity floor of globular clusters, which supports the growing evidence for the existence of lower-metallicity globular clusters in the early Universe. A third star (P180956, [Fe/H] $\sim-2$) has low [Na,Ca/Mg] and very low [Ba/Fe] for its metallicity, which are consistent with formation in a system polluted by only one or a few low-mass supernovae. Interestingly, its orbit is confined to the Galactic plane, like other very metal-poor stars found in the literature, which have been associated with the earliest building blocks of the Milky Way.

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