论文标题
我们银河系早期形成历史的时间分辨图片
A time-resolved picture of our Milky Way's early formation history
论文作者
论文摘要
我们的银河系的形成可以被定性地解析为不同的阶段，从而导致其结构上不同的恒星种群：光晕和磁盘成分。揭示了银河系组件的定量总体图片，等待着非常精确的年龄的大量恒星样本。在这里，我们报告使用次巨星对这种样品的分析。我们发现恒星年龄金属分布P（年龄，金属性）分为两个几乎不相交的部分，分别在8 Gyr处分开。年轻人反映了静态银河盘形成的后期，并有明显的证据证明了恒星径向轨道迁移；另一个反映了较早的阶段，当形成恒星光环和旧的alpha-process-Enhhathanced（厚）磁盘时。我们的结果表明，银河系旧（厚）磁盘的形成始于13 Gyr，大爆炸后仅在0.8 Gyr，而两个Gigayears则比内部银河系的最终组装早。这些恒星中的大多数是11 Gyr，当时Gaia-Sausage-Ecceladus卫星与我们的银河系合并时。在接下来的5--6 Gyr中，银河系经历了连续的化学元件富集，最终达到10倍，而星形的气体则保持了充分的混杂状态。
The formation of our Milky Way can be parsed qualitatively into different phases that resulted in its structurally different stellar populations: the halo and the disk components. Revealing a quantitative overall picture of the Galactic assembly awaits a large sample of stars with very precise ages. Here we report an analysis of such a sample using subgiant stars. We find that the stellar age-metallicity distribution p(age, metallicity) splits into two almost disjoint parts, separated at 8 Gyr. The younger reflecting a late phase of quiescent Galactic disk formation with manifest evidence for stellar radial orbit migration; the other reflecting the earlier phase, when the stellar halo and the old alpha-process-enhanced (thick) disk formed. Our results indicate that the formation of the Galactic old (thick) disk started 13 Gyr ago, only 0.8 Gyr after the Big Bang, and two Gigayears earlier than the final assembly of the inner Galactic halo. Most of these stars formed 11 Gyr ago, when the Gaia-Sausage-Enceladus satellite merged with our Galaxy. Over the next 5--6 Gyr, the Galaxy experienced continuous chemical element enrichment, ultimately by a factor of 10, while the star-forming gas managed to stay well-mixed.
