AN EXTREMELY CARBON-RICH, EXTREMELY METAL-POOR STAR IN THE SEGUE 1 SYSTEM
AN EXTREMELY CARBON-RICH, EXTREMELY METAL-POOR STAR IN THE SEGUE 1 SYSTEM
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SEGUE 1 系统中碳含量极高、金属含量极少的恒星
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
A. Frebel
中科院分区：
文献类型：
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作者：
J. Norris;G. Gilmore;R. Wyse;D. Yong;A. Frebel
我们报告的高分辨率，高信噪比，光谱的一个极端贫金属，非常富C的红巨星，赛格1-7，在赛格1-描述的文献中，作为一个异常扩展的球状星团或超微弱的矮星系。Seg 1-7的径向速度与Segue 1的系统速度精确一致，其化学丰度特征为[Fe/H] =-3.52，[C/Fe] =+2.3，[N/Fe] =+0.8，[Na/Fe] =+0.53，[Mg/Fe]=+0.94，[Al/Fe]=+0.23，而[Ba/Fe] < −1.0，类似于罕见且神秘的银河系晕天体CEMP-no（富碳、极贫金属，重中子捕获元素没有增强（超过太阳比））。这是银河系“卫星”中的第一颗星星，它明确地位于青木等人在（[C/Fe]，[Fe/H]）平面上场晕星双峰分布的贫金属、富C分支上。现有的数据只允许我们将Seg 1-7识别为超微弱矮星系的成员或Sgr矮球状星系的碎片。无论哪种情况，这都表明在极低的丰度下，[Fe/H ] <-3.0，星星的形成和相关的化学演化在场晕和卫星系统的祖先中进行得相似。通过扩展，这与最近的其他建议是一致的，即最贫金属的矮球状和超暗矮卫星是银河系外晕的组成部分。
We report the analysis of high-resolution, high signal-to-noise ratio, spectra of an extremely metal-poor, extremely C-rich red giant, Seg 1–7, in Segue 1—described in the literature alternatively as an unusually extended globular cluster or an ultra-faint dwarf galaxy. The radial velocity of Seg 1–7 coincides precisely with the systemic velocity of Segue 1, and its chemical abundance signature of [Fe/H] = −3.52, [C/Fe] = +2.3, [N/Fe] = +0.8, [Na/Fe] = +0.53, [Mg/Fe] = +0.94, [Al/Fe] = +0.23, and [Ba/Fe] < −1.0 is similar to that of the rare and enigmatic class of Galactic halo objects designated CEMP-no (carbon-rich, extremely metal-poor with no enhancement (over solar ratios) of heavy neutron-capture elements). This is the first star in a Milky Way “satellite” that unambiguously lies on the metal-poor, C-rich branch of the Aoki et al. bimodal distribution of field halo stars in the ([C/Fe], [Fe/H])-plane. Available data permit us only to identify Seg 1–7 as a member of an ultra-faint dwarf galaxy or as debris from the Sgr dwarf spheroidal galaxy. In either case, this demonstrates that at extremely low abundance, [Fe/H ] <−3.0, star formation and associated chemical evolution proceeded similarly in the progenitors of both the field halo and satellite systems. By extension, this is consistent with other recent suggestions that the most metal-poor dwarf spheroidal and ultra-faint dwarf satellites were the building blocks of the Galaxy's outer halo.
DOI：
10.1086/590336
发表时间：
2008-05
期刊：
The Astrophysical Journal
影响因子：
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作者：
N. Martin;J. D. de Jong;H. Rix
通讯作者：
N. Martin;J. D. de Jong;H. Rix