The Extragalactic Origin of the Arcturus Group
The Extragalactic Origin of the Arcturus Group
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大角星群的河外起源
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
K. Freeman
中科院分区：
文献类型：
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作者：
J. Navarro;A. Helmi;K. Freeman
我们重新分析了与大角星运动学相关的恒星群，并确认它们构成了一个特殊的贫金属恒星群，具有相似的远心半径，共同的角动量和独特的金属丰度模式。这些属性是一致的预期一组恒星起源于一个破碎的卫星碎片。大角星群在比尔斯等人的星表和其他太阳附近贫金属恒星的汇编中非常突出。它的角动量看起来太低，不可能是由银河棒引起的动力学扰动引起的，并且与吉尔摩、怀斯和诺里斯在银河平面之上和之下发现的运动学上奇特的恒星群相吻合：大角星群很可能是这种恒星群的太阳邻域延伸。需要进一步的分析来证实我们的提议，大角星和夜空中一些最亮的恒星可能是在银河系之外形成的。然而，验证大角星群的河外起源将支持星系形成的分层模型中设想的吸积事件的普遍性，并表明早期合并可能贡献了银河系盘中很大一部分古老和缺乏金属的恒星。
We reanalyze the group of stars associated kinematically with Arcturus and confirm that they constitute a peculiar grouping of metal-poor stars with similar apocentric radius, common angular momentum, and distinct metal abundance patterns. These properties are consistent with those expected for a group of stars originating from the debris of a disrupted satellite. The Arcturus group stands out clearly in the catalog of Beers et al. and in other compilations of metal-poor stars in the solar neighborhood. Its angular momentum appears too low to arise from dynamical perturbations induced by the Galactic bar and coincides with that of the kinematically peculiar population of stars identified above and below the Galactic plane by Gilmore, Wyse, & Norris: the Arcturus group is in all likelihood the solar neighborhood extension of such population. Further analysis is needed to confirm our proposal that Arcturus, together with some of the brightest stars in the night sky, may have formed beyond the confines of the Galaxy. However, validating the extragalactic origin of the Arcturus group would lend support to the prevalence of accretion events envisioned in hierarchical models of galaxy formation and would suggest that early mergers may have contributed a substantial fraction of the old and metal-deficient stars in the Galactic disk.