论文标题
萨克斯坦矮人球形星系中极为金属贫困的星星的化学丰度分析
Chemical abundance analysis of extremely metal-poor stars in the Sextans dwarf spheroidal galaxy
论文作者
论文摘要
银河系周围的矮星系的金属贫困组件可能是银河光环结构的构件的残余物。当前观察到的低质量恒星预计在星系形成的早期阶段中将在化学均匀的簇中形成。他们应该已经瓦解，并且应该以大量散布比在银河系恒星中的某些元素（例如SR/BA）的大量散射。然而，预计化学丰度比在矮星系中聚集在非常贫穷的星星中，因为在很早的早期阶段，单个星系中形成的簇数量预计将非常有限。我们检查了萨克斯坦矮星系中SR和BA的丰度比率的可能聚类，以测试聚类恒星形成场景。我们总共研究了11个元素（C，MG，CA，SC，TI，CR，MN，NI，NI，ZN，SR，BA），在Sextans Dwarf Galaxy中的五颗星中。先前的研究表明，这些含量比相似。在这项研究中，我们专注于SR与BA的丰度比。该观察结果基于使用Subaru望远镜高分散光谱仪的高分辨率光谱学（R = 40 000）。萨克斯坦矮星系星的$α$/fe丰度比的分布略低于银河晕圈中恒星值的平均值。五个金属贫困恒星的SR/BA丰度比非常吻合，与在金属贫乏的光晕恒星中看到的[SR/BA]扩散相比，这种结块是独特的。我们发现，如果六颗星具有类似于光环恒星的SR和BA丰度的分布，那么这种结块的可能性很小。
Metal-poor components of dwarf galaxies around the Milky Way could be remnants of the building blocks of the Galactic halo structure. Low-mass stars that are currently observed as metal-poor stars are expected to have formed in chemically homogeneous clusters in the early phases of galaxy formation. They should have already disintegrated and should exhibit large scatter in abundance ratios of some sets of elements (e.g., Sr/Ba) in the Milky Way field stars. However, chemical abundance ratios are expected to cluster in very metal-poor stars in dwarf galaxies because the number of clusters formed in individual galaxies in the very early phase is expected to be quite limited. We examine the possible clustering of abundance ratios of Sr and Ba in the Sextans dwarf galaxy to test for the clustering star formation scenario. We investigate a total of 11 elements (C, Mg, Ca, Sc, Ti, Cr, Mn, Ni, Zn, Sr, Ba) in five stars in the Sextans dwarf galaxy. Previous studies suggest that these have similar abundance ratios. In this study, we focus on the abundance ratio of Sr to Ba. The observations are based on high-resolution spectroscopy (R = 40 000) using the Subaru Telescope High Dispersion Spectrograph. The distribution of $α$/Fe abundance ratios of the Sextans dwarf galaxy stars is slightly lower than the average of the values of stars in the Galactic halo. The Sr/Ba abundance ratios for the five metal-poor stars are in good agreement, and this clumping is distinctive compared to the [Sr/Ba] spread seen in the metal-poor halo stars. We find that the probability of such clumping is very small if the Sextans stars have distributions of Sr and Ba abundances similar to halo stars.
