银河系核星团中巨星异常成分的证据
Evidence against anomalous compositions for giants in the Galactic Nuclear Star Cluster
摘要：
最近在银河系中心核星团的冷M巨星中发现了非常强的Sc I线。将这些解释为银河系中心异常高的钪丰度将意味着核星团的独特增强特征和化学演化历史，以及对这些物体化学富集模型的潜在测试。我们目前的高分辨率K波段光谱（NIRSPEC/凯克II）的冷M巨星位于太阳附近，并比较它们与M巨星的光谱在核星团。我们清楚地确定强Sc I线在我们的太阳附近的样本，以及在核星团的样本。因此，M巨星的强Sc I线并不是核星团中恒星所独有的，我们认为，强线是目前逃脱精确理论建模的线形成过程的一个属性。我们进一步得出结论，对于巨恒星的有效温度低于约3800 K，这些Sc I线不应该被用于推导钪丰度在任何天体物理环境中，直到我们更好地了解这些线是如何形成的。我们还讨论了钒，钛和钇的光谱中确定的线，这表明在3500 K有效温度以下的强度类似的显着增加。
英文摘要：
Very strong Sc I lines have been found recently in cool M giants in the Nuclear Star Cluster in the Galactic Center. Interpreting these as anomalously high scandium abundances in the Galactic Center would imply a unique enhancement signature and chemical evolution history for nuclear star clusters, and a potential test for models of chemical enrichment in these objects. We present high resolution K-band spectra (NIRSPEC/Keck II) of cool M giants situated in the solar neighborhood and compare them with spectra of M giants in the Nuclear Star Cluster. We clearly identify strong Sc I lines in our solar neighborhood sample as well as in the Nuclear Star Cluster sample. The strong Sc I lines in M giants are therefore not unique to stars in the Nuclear Star Cluster and we argue that the strong lines are a property of the line formation process that currently escapes accurate theoretical modeling. We further conclude that for giant stars with effective temperatures below approximately 3800 K these Sc I lines should not be used for deriving the scandium abundances in any astrophysical environment until we better understand how these lines are formed. We also discuss the lines of vanadium, titanium, and yttrium identified in the spectra, which demonstrate a similar striking increase in strength below 3500 K effective temperature.
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