The age–metallicity structure of the Milky Way disc using APOGEE
The age–metallicity structure of the Milky Way disc using APOGEE
复制标题
DOI：
10.1093/mnras/stx1774
复制
发表时间：
2017-05
影响因子：
4.8
通讯作者：
J. Mackereth;J. Bovy;R. Schiavon;G. Zasowski;K. Cunha;P. Frinchaboy;A. G. Pérez;M. Hayden;
中科院分区：
文献类型：
--
作者：
J. Mackereth;J. Bovy;R. Schiavon;G. Zasowski;K. Cunha;P. Frinchaboy;A. G. Pérez;M. Hayden;
对银河系盘中恒星群结构的测量对星系形成和演化的模型提出了基本的限制。以前，人们根据几何和/或化学上定义的群体来研究圆盘的结构，但基于恒星年龄的分解提供了与圆盘历史更直接的联系，并对理论产生了更强的约束。在这里，我们使用来自斯隆数字天空调查的31244颗红巨星分支恒星的位置、丰度和年龄，横跨3<；RGC<；15kpc，来剖析圆盘在低和高[α/Fe]下的单年龄和单[Fe/H]群体。对于每个种群，在年龄为2Gyr和[Fe/H]<；0.1Dex的情况下，我们测量了结构和表面质量密度贡献。我们发现，低[α/Fe]单龄种群很好地符合破裂指数，该指数增加到一个峰值半径，然后减小。我们发现，随着年龄的增长，这一分布变得更宽，在这里被解释为盘加热和径向迁移的新信号。高[α/Fe]种群在所考虑的径向范围内符合单指数分布，平均标尺长度为1.9±0.1kpc。我们发现，在R0处，高[α/Fe]种群对低[α/Fe]种群的相对贡献为f-α=18%±5%；高[α/Fe]种群在老年时贡献了大部分质量，而低[α/Fe]种群在年轻时贡献了大部分质量。低[α/Fe]和高[Fe/Fe]种群在中等[Fe/H]时年龄重叠，尽管两者在[Fe/H]的整个范围内都在R0处贡献质量。质量加权尺度高度的赫兹分布是一个平稳下降的指数函数。高[α/Fe]种群比低[α/Fe]种群厚，平均赫兹随着年龄的增长而稳步增加，在200到600pC之间。
The measurement of the structure of stellar populations in the Milky Way disc places fundamental constraints on models of galaxy formation and evolution. Previously, the disc’s structure has been studied in terms of populations defined geometrically and/or chemically, but a decomposition based on stellar ages provides a more direct connection to the history of the disc, and stronger constraint on theory. Here, we use positions, abundances and ages for 31 244 red giant branch stars from the Sloan Digital Sky Survey (SDSS)-APOGEE survey, spanning 3 < Rgc < 15 kpc, to dissect the disc into mono-age and mono-[Fe/H] populations at low and high [α/Fe]. For each population, with age < 2 Gyr and [Fe/H] < 0.1 dex, we measure the structure and surface-mass density contribution. We find that low [α/Fe] mono-age populations are fit well by a broken exponential, which increases to a peak radius and decreases thereafter. We show that this profile becomes broader with age, interpreted here as a new signal of disc heating and radial migration. High [α/Fe] populations are well fit as single exponentials within the radial range considered, with an average scalelength of 1.9 ± 0.1 kpc. We find that the relative contribution of high to low [α/Fe] populations at R0 is f� = 18 per cent ± 5 per cent; high [α/Fe] contributes most of the mass at old ages, and low [α/Fe] at young ages. The low and high [α/Fe] populations overlap in age at intermediate [Fe/H], although both contribute mass at R0 across the full range of [Fe/H]. The mass-weighted scaleheight hZ distribution is a smoothly declining exponential function. High [α/Fe] populations are thicker than low [α/Fe], and the average hZ increases steadily with age, between 200 and 600 pc.