利用Gaia-ESO巡天追踪早期银河系薄盘
Tracing the early Milky Way thin disc with the Gaia-ESO Survey
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中文总结 AI 辅助
本研究利用Gaia-ESO巡天等数据，在1784颗turn-off星中发现一颗具有类薄盘运动学特征的贫金属老星，其化学性质异于标准薄盘，为研究早期盘轨道贫金属星族提供了基准。
中文摘要 AI 辅助
薄盘轨道上贫金属星的起源仍是星系考古学中的一个悬而未决的问题，也为银河系薄盘形成的最早期阶段提供了重要约束。我们旨在利用Gaia DR3轨道参数、光谱信息、等时线年龄以及详细的化学丰度，对Gaia-ESO巡天中观测到的、具有类薄盘运动学特征的贫金属星进行识别与表征。在1784颗 turn-off 星中，我们识别出一颗贫金属候选体，其[Fe/H] = -1.38，处于动力学冷的顺行轨道上，具有低偏心率、高方位速度（$V_ϕ$约为220 km/s）、大角动量以及低垂直作用量的特征。然而在化学组成上，它与标准薄盘明显不同：它是α元素增强的，[Mg/Fe] = +0.58，[α/Fe] = +0.48，呈现出较低的[Y/Mg] = -0.58比值，且在[Al/Fe]-[Mg/Mn]平面上位于贫金属序上。这颗恒星的年龄估计也很老，最概然值约为102亿年。它的性质表明它并非标准薄盘的典型成员，反而可能与年老薄盘、弱金属厚盘或者顺行的晕相关星族有关。该天体为研究类盘轨道上的早期贫金属星族提供了有用的基准。
英文摘要
The origin of metal-poor stars on thin-disc-like orbits remains an open question in Galactic archaeology and provides important constraints on the earliest phases of Milky Way disc formation. We aim to identify and characterise metal-poor stars with thin-disc-like kinematics observed in the Gaia-ESO Survey, using Gaia DR3 orbital parameters, spectroscopic information, isochrone ages, and detailed chemical abundances. Out of 1784 turn-off stars, we identify one metal-poor candidate with [Fe/H] = -1.38 on a dynamically cold, prograde orbit, with low eccentricity, high azimuthal velocity ($V_ϕ$ approximately 220 km/s), large angular momentum and low vertical action. Chemically, however, it is clearly distinct from the canonical thin disc: it is $α$-enhanced, with [Mg/Fe] = +0.58 and [$α$/Fe] = +0.48, shows a low [Y/Mg] = -0.58 ratio, and lies on the metal-poor sequence in the [Al/Fe]-[Mg/Mn] plane. The star also has an old age estimate, with a most probable value of about 10.2 Gyr. Its properties suggest that it is not a typical member of the canonical thin disc. Instead, it may be associated with the old thin disc, the metal-weak thick disc, or prograde halo-related populations. This object provides a useful benchmark for studying early metal-poor populations on disc-like orbits.
