A Tale of Two Disks: Mapping the Milky Way with the Final Data Release of APOGEE
A Tale of Two Disks: Mapping the Milky Way with the Final Data Release of APOGEE
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DOI：
10.3847/1538-4357/ace9b8
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发表时间：
2023-07
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影响因子：
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通讯作者：
J. Imig;Cathryn Price;J. Holtzman;Alexander Stone-Martinez;S. Majewski;D. Weinberg;Jennifer Johnson-Jennifer-Johns
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文献类型：
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作者：
J. Imig;Cathryn Price;J. Holtzman;Alexander Stone-Martinez;S. Majewski;D. Weinberg;Jennifer Johnson-Jennifer-Johns
我们利用阿帕奇点天文台银河系演化实验调查的最终数据发布（DR17）中的66,496颗红巨星样本，绘制了银河系盘的新地图，显示了金属丰度（[Fe/H]）、α-元素丰度（[Mg/Fe]）和恒星年龄的分布。我们测量了径向和垂直梯度，量化了年龄和金属丰度的分布函数，并独立探索了整个银河系中低α盘、高α盘和总人口的化学时钟关系。低α盘呈现负的径向金属丰度梯度（- 0.06±0.001 index kpc−1），随距离背板的远近而变平。高α盘在金属丰度和年龄上呈现平坦的径向梯度，几乎遍及盘的所有位置。年龄和金属丰度分布函数从银河系内部的负偏向大半径处的正偏转变。[Mg/Fe] - [Fe/H]平面和[Mg/Fe] -年龄关系的显著双峰性贯穿整个圆盘。年龄估计值的典型不确定性为对数（年龄）的~ 0.15，并可能受到额外的系统误差的影响，这对从该样本得出的结论施加了限制。然而，这些结果对星系演化模型起到了关键的约束作用，限制了哪些物理过程在银河系盘的形成中发挥了主导作用。我们讨论了径向迁移如何预测在太阳附近和外盘观察到的许多趋势，但需要一个额外的更戏剧性的演化历史，如多落模型或合并事件，来解释银河系其他地方的化学和年龄双峰性。
We present new maps of the Milky Way disk showing the distribution of metallicity ([Fe/H]), α-element abundances ([Mg/Fe]), and stellar age, using a sample of 66,496 red giant stars from the final data release (DR17) of the Apache Point Observatory Galactic Evolution Experiment survey. We measure radial and vertical gradients, quantify the distribution functions for age and metallicity, and explore chemical clock relations across the Milky Way for the low-α disk, high-α disk, and total population independently. The low-α disk exhibits a negative radial metallicity gradient of −0.06 ± 0.001 dex kpc−1, which flattens with distance from the midplane. The high-α disk shows a flat radial gradient in metallicity and age across nearly all locations of the disk. The age and metallicity distribution functions shift from negatively skewed in the inner Galaxy to positively skewed at large radius. Significant bimodality in the [Mg/Fe]–[Fe/H] plane and in the [Mg/Fe]–age relation persist across the entire disk. The age estimates have typical uncertainties of ∼0.15 in log(age) and may be subject to additional systematic errors, which impose limitations on conclusions drawn from this sample. Nevertheless, these results act as critical constraints on galactic evolution models, constraining which physical processes played a dominant role in the formation of the Milky Way disk. We discuss how radial migration predicts many of the observed trends near the solar neighborhood and in the outer disk, but an additional more dramatic evolution history, such as the multi-infall model or a merger event, is needed to explain the chemical and age bimodality elsewhere in the Galaxy.