浴火重生：金属丰度依赖的恒星形成间隙分裂了银河系的α序列
Rising from the Ashes: A Metallicity-Dependent Star Formation Gap Splits the Milky Way's alpha-Sequences
AI总结：
本文提出银河系α序列双峰源于金属丰度窄区间内约300 Myr的恒星形成停顿，并模拟表明z~2处与Gaia-Sausage-Enceladus卫星并合可触发此间隙。
摘要：
恒星元素丰度分布编码了银河系中气相丰度的历史。在没有大量无偏的高精度恒星年龄样本的情况下，这段历史的精确时间和性质必须从丰度中推断。在[α/Fe]-[Fe/H]二维平面上，现在清楚的是存在两个独立的星族——低α序列和高α序列。我们提出，在一个狭窄的金属丰度区间内，恒星形成的短暂（约300 Myr）停顿，假设气相[α/Fe]快速下降，可以导致该金属丰度下[α/Fe]分布的双峰。使用高红移星系并合的理想化设置模拟，我们表明在z~2处与Gaia-Sausage-Enceladus卫星星系的并合是触发银河系中这种间隙的一种可能方式。这种机制也可能在非并合情景中运作。我们预测在固定的[Fe/H]下，在α双峰性显著的（[Fe/H]<~-0.2）区域，恒星年龄存在约300 Myr的间隙。
英文摘要：
The elemental abundance distribution of stars encodes the history of the gas-phase abundance in the Milky Way. Without a large, unbiased sample of highly precise stellar ages, the exact timing and nature of this history must be inferred from the abundances. In the two-dimensional plane of [alpha/Fe]-[Fe/H], it is now clear that two separate populations exist -- the low-alpha and high-alpha sequences. We propose that a brief (~300 Myr) halt in star formation within a narrow metallicity bin can lead to a bimodal [alpha/Fe] distribution at that metallicity, assuming a rapidly declining gas phase [alpha/Fe]. Using simulations of an idealized setup of a high-z galaxy merger, we show that the merger with the Gaia-Sausage-Enceladus satellite at z~2 is one possible way to trigger such a gap in the Milky Way. This mechanism may also operate in non-merger scenarios. We predict a ~300 Myr gap in stellar ages at a fixed [Fe/H] where the alpha-bimodality is prominent ([Fe/H]<~-0.2)
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