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arXiv 1901.02563astro-ph.SRastro-ph.GA
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玉夫座矮球状星系红巨星C、N和Na丰度的研究

An investigation of C, N and Na abundances in red giant stars of the Sculptor dwarf spheroidal galaxy

C. Salgado, G. S. Da Costa, J. E. Norris, D. Yong

备注：
24 pages, 17 figures, 8 tables
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摘要：

银河系球状星团（GGC）中轻元素丰度的星-星变化是恒星天体物理学中的一个重要问题，其成因至今尚未得到很好的解释。虽然轻元素丰度的变化在球状星团中很常见，但在星系晕场总体中却比较罕见。然而，鲜为人知的是，在其他环境中，如矮球状（dSph）星系的丰度异常的发生。因此，我们研究了反相关和双峰的CH和CN带强度，这是GGC的丰度变化的标志，在红巨星的Sculptor矮球状星系的光谱。利用Na~D线的光谱，结合5个GGC（NGC 288，1851，6752，6809和7099）的相似光谱，我们还研究了Sculptor红巨星样品中CN和Na之间的相关性。我们的结果表明，在我们的Sculptor样本中不存在类似于GGC中所见的变化。相反，我们发现CH和CN之间存在弱的正相关性，而Na和CN之间没有相关性。我们还揭示了一个不足的[Na/Fe]的雕塑星相对于GGC的值，这一结果是一致的，与以前的工作dSph星系。结果加强了明显需要一个高恒星密度的环境，以产生轻元素丰度的变化。

英文摘要：

The origin of the star-to-star abundance variations found for the light elements in Galactic globular clusters (GGCs) is not well understood, which is a significant problem for stellar astrophysics. While the light element abundance variations are very common in globular clusters, they are comparatively rare in the Galactic halo field population. However, little is known regarding the occurrence of the abundance anomalies in other environments such as that of dwarf spheroidal (dSph) galaxies. Consequently, we have investigated the anti-correlation and bimodality of CH and CN band strengths, which are markers of the abundance variations in GGCs, in the spectra of red giants in the Sculptor dwarf spheroidal galaxy. Using spectra at the Na~D lines, informed by similar spectra for five GGCs (NGC 288, 1851, 6752, 6809 and 7099), we have also searched for any correlation between CN and Na in the Sculptor red giant sample. Our results indicate that variations analogous to those seen in GGCs are not present in our Sculptor sample. Instead, we find a weak positive correlation between CH and CN, and no correlation between Na and CN. We also reveal a deficiency in [Na/Fe] for the Sculptor stars relative to the values in GGCs, a result which is consistent with previous work for dSph galaxies. The outcomes reinforce the apparent need for a high stellar density environment to produce the light element abundance variations.

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