Title: The chemical enrichment histories across the Milky Way disk Show Chinese title

Title: 银河系盘的化学富集历史

Abstract: The variation of metal production over time and its dilution in the interstellar medium depend on the star formation and gas accretion rates. Measuring age-chemistry relations across the Milky Way disk provides key constraints on the gas accretion and star formation histories, and offers insight into the birth locations of stars. We present a study based on a sample of nearly 30000 dwarf stars from the APOGEE DR17 survey within 2 kpc of the Sun, for which we measure accurate ages. Various parameter combinations are tested to optimize stellar age determination from isochrones. The resulting age-chemistry relations for a selected subsample of 12000 stars are interpreted with the aid of a chemical evolution model. The data reveal a well-defined, tight thick disk sequence, characterized by high [alpha/Fe], subsolar metallicities, and ages older than 8 Gyr. The thin disk, with lower [alpha/Fe] and younger ages, exhibits a wide spread in metallicity at all ages, with apparent structures. Dividing the sample by guiding radius into inner, intermediate, and outer disks shows distinct chemical evolution patterns. The inner disk displays a monotonic, homogeneous chemical evolution with little dispersion, while the outer disk shows little metallicity increase over the past 8 Gyr. The solar neighborhood appears as a mixture, not only due to stellar migration but also because the chemical evolution of the ISM in this intermediate region results from the mixing of gas from the inner and outer disks. In particular, we demonstrate that the solar vicinity experienced a decrease in the mean ISM metallicity 7-9 Gyr ago. A plausible explanation involves a radial inflow of lower-metallicity gas from the outer disk at that time, which diluted the gas leftover by the thick disk formation, contributing to the observed metallicity gradient in the intermediate region. Show Chinese abstract

Abstract: 金属产量随时间的变化及其在星际介质中的稀释取决于恒星形成率和气体吸积率。 测量银河系盘中年龄-化学成分关系为气体吸积和恒星形成历史提供了关键约束，并有助于了解恒星的诞生位置。 我们基于APOGEE DR17调查中距离太阳2 kpc范围内的近30000颗矮星样本进行了一项研究，其中我们测定了精确的年龄。 测试了各种参数组合以优化从等时线确定恒星年龄。 利用化学演化模型，对选定的12000颗恒星的年龄-化学成分关系进行了解释。 数据揭示了一个明确且紧密的厚盘序列，其特征是高[alpha/Fe]、亚太阳金属丰度以及年龄超过8 Gyr。 薄盘具有较低的[alpha/Fe]和较年轻的年龄，在所有年龄上都表现出广泛的金属丰度分布，并显示出明显的结构。 按引导半径将样本分为内盘、中间盘和外盘，显示了不同的化学演化模式。 内盘表现出单调且均匀的化学演化，分散性很小，而外盘在过去8 Gyr内金属丰度几乎没有增加。 太阳邻域表现为一种混合状态，不仅由于恒星迁移，还因为该中间区域的星际介质（ISM）的化学演化是由内盘和外盘气体混合产生的。 特别是，我们证明太阳邻域在7-9 Gyr前经历了平均ISM金属丰度的下降。 一个可能的解释是在当时发生了来自外盘的低金属丰度气体的径向流入，这稀释了厚盘形成后剩余的气体，从而导致了中间区域观测到的金属丰度梯度。