论文标题
按时间顺序与银河系的早期大会约会
Chronologically dating the early assembly of the Milky Way
论文作者
论文摘要
标准宇宙学模型（$λ$ -CDM）预测，星系是通过宇宙时间标准$^{1,2} $在层次组件上构建的。银河系与其他盘状星系一样，在早期历史上进行了暴力合并和小型卫星星系的积聚。感谢Gaia-Dr2 $^3 $和光谱调查$^4 $，已经确定了此类合并的出色残余物$^{5-7} $。此类事件的时间顺序对揭示高红移时银河系的形成和演变至关重要，但是由于在为这些最古老的恒星获得精确年龄的困难，迄今为止，它一直具有挑战性。在这里，我们将Asterosology（恒星振荡的研究）与运动学和化学丰度相结合，以估计由$ \ Mathit {Kepler} $ Space Mission Mission Mission $^8 $观察到的精确的恒星年龄（$ \ sim $ 11％）。至关重要的是，该样本不仅包括银河系内形成的一些最古老的恒星，还包括外部形成并随后形成的恒星。利用这种分辨率在年龄上，我们提供了令人信服的证据，以支持银河系在卫星Gaia-eceLadus/sausage的落下之前已经形成了大量的恒星（现在主要属于其厚盘）（现在主要属于其厚盘）。
The standard cosmological model ($Λ$-CDM) predicts that galaxies are built through hierarchical assembly on cosmological timescales$^{1,2}$. The Milky Way, like other disc galaxies, underwent violent mergers and accretion of small satellite galaxies in its early history. Thanks to Gaia-DR2$^3$ and spectroscopic surveys$^4$, the stellar remnants of such mergers have been identified$^{5-7}$. The chronological dating of such events is crucial to uncover the formation and evolution of the Galaxy at high redshift, but it has so far been challenging owing to difficulties in obtaining precise ages for these oldest stars. Here we combine asteroseismology -- the study of stellar oscillations -- with kinematics and chemical abundances, to estimate precise stellar ages ($\sim$ 11%) for a sample of stars observed by the $\mathit{Kepler}$ space mission$^8$. Crucially, this sample includes not only some of the oldest stars that were formed inside the Galaxy, but also stars formed externally and subsequently accreted onto the Milky Way. Leveraging this resolution in age, we provide compelling evidence in favour of models in which the Galaxy had already formed a substantial population of its stars (which now reside mainly in its thick disc) before the in-fall of the satellite galaxy Gaia-Enceladus/Sausage$^{5,6}$ around 10 billions years ago
