文章基本信息

标题：Medium-resolution Spectroscopy of Red Giant Branch Stars in ω Centauri
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作者：Deokkeun An ; Young Sun Lee ; Jae In Jung 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2017
卷号：154
期号：4
页码：1-7
DOI：10.3847/1538-3881/aa8364
语种：English
出版社：American Institute of Physics
摘要：We present [Fe/H] and [Ca/Fe] of ~600 red giant branch (RGB) members of the globular cluster Omega Centauri (). We collect medium-resolution () spectra using the Blanco 4 m telescope at the Cerro Tololo Inter-American Observatory equipped with Hydra, the fiber-fed multi-object spectrograph. We demonstrate that blending of stellar light in optical fibers severely limits the accuracy of spectroscopic parameters in the crowded central region of the cluster. When photometric temperatures are taken in the spectroscopic analysis, our kinematically selected cluster members, excluding those that are strongly affected by flux from neighboring stars, include relatively fewer stars at intermediate metallicity () than seen in the previous high-resolution survey for brighter giants in Johnson & Pilachowski. As opposed to the trend of increasing [Ca/Fe] with [Fe/H] found by those authors, our [Ca/Fe] estimates, based on Ca ii H & K measurements, show essentially the same mean [Ca/Fe] for most of the metal-poor and metal-intermediate populations in this cluster, suggesting that mass- or metallicity-dependent SN II yields may not be necessary in their proposed chemical evolution scenario. Metal-rich cluster members in our sample show a large spread in [Ca/Fe], and do not exhibit a clear bimodal distribution in [Ca/Fe]. We also do not find convincing evidence for a radial metallicity gradient among RGB stars in .
关键词：globular clusters: individual (omega Centauri) ; stars: abundances