论文标题
CEMP和C-Normal恒星中的经验金属示踪剂
An empirical metallicity tracer in CEMP and C-normal stars
论文作者
论文摘要
在碳增强金属贫困（CEMP）恒星的低分辨率光谱中得出金属性[Fe/H]是一项繁琐的任务，由于线条混合物的大量混合物，通常会导致[Fe/H]超过0.25DEX的不确定性。 CEMP恒星的数量随[Fe/H]的减少而增加，其中一些恒星已知是真正的第二代Halo恒星。因此，知道它们的[Fe/H]对于追踪银河系的形成和化学演化很重要。在这里，我们旨在通过避免与混合物相关的问题来改善低分辨率光谱中的[Fe/H]测量值。我们在低金属率的情况下改善了此类光谱中的化学标记。我们开发了一种在CEMP（和C-正常）恒星中得出[Fe/H]的经验方法，该恒星与强线的等效宽度（EW）相关联，这些宽度（EW）在低分辨率的金属贫穷光谱中仍可检测到。发现最好的[Fe/H]示踪剂是Cr I和Ni I，它们在没有分子带的光谱区域都显示出强的过渡（〜5200-6800A介于〜5200-6800A之间，大多数调查都可以访问该区域）。我们为矮人和巨人提供了不同的关系。该关系在范围〜-3 <[fe/h] <-0.5和10 <ew <800mA（cr）或[fe/h]> -3.2和ew> 5mA（ni）中是有效的，取决于元素和线以及恒星进化阶段。经验关系对于CEMP和C-正常恒星都是有效的，并且已被证明是约400颗恒星（主要是巨人）的准确示踪剂。根据样品和分辨率的不同，金属的准确性在〜0.2之内，并且经验关系在0.05-0.1dex以内具有鲁棒性。我们的关系将改善未来调查中的金属性确定，这将遇到大量的CEMP恒星，并且将大大加快确定[Fe/H]的过程，因为与与许多混合FE线相比，相对干净的区域中只需要在相对清洁的区域中测量EWS。擦伤。
Deriving the metallicity, [Fe/H], in low-resolution spectra of carbon-enhanced metal-poor (CEMP) stars is a tedious task that, owing to the large number of line blends, often leads to uncertainties on [Fe/H] exceeding 0.25dex. The CEMP stars increase in number with decreasing [Fe/H] and some of these are known to be bona fide second generation halo stars. Hence, knowing their [Fe/H] is important for tracing the formation and chemical evolution of the Galaxy. Here, we aim to improve the [Fe/H] measurements in low-resolution spectra by avoiding issues related to blends. We improve our chemical tagging in such spectra at low metallicities. We developed an empirical way of deriving [Fe/H] in CEMP (and C-normal) stars that relates the equivalent width (EW) of strong lines, which remain detectable in lower-resolution, metal-poor spectra. The best [Fe/H] tracers are found to be Cr I and Ni I, which both show strong transitions in spectral regions that are free of molecular bands (between ~5200-6800A, a region accessible to most surveys). We derive different relations for dwarfs and giants. The relations are valid in the ranges ~-3<[Fe/H]<-0.5 and 10<EW<800mA (Cr) or [Fe/H]>-3.2 and EW>5mA (Ni), depending on the element and line as well as the stellar evolutionary stage. The empirical relations are valid for both CEMP and C-normal stars and have been proven to be accurate tracers in a sample of ~400 stars (mainly giants). The metallicities are accurate to within ~0.2 depending on the sample and resolution, and the empirical relations are robust to within 0.05-0.1dex. Our relations will improve the metallicity determination in future surveys, which will encounter a large number of CEMP stars, and will greatly speed up the process of determining [Fe/H] as the EWs only need to be measured in two or three lines in relatively clean regions compared to dealing with numerous blended Fe lines. Abrigded.
