From dawn till disk: Milky Way’s turbulent youth revealed by the APOGEE+Gaia data
From dawn till disk: Milky Way’s turbulent youth revealed by the APOGEE+Gaia data
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从黎明到盘面：APOGEE+盖亚数据揭示了银河系动荡的青春
DOI：
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发表时间：
2022
影响因子：
4.8
通讯作者：
A. Kravtsov
中科院分区：
文献类型：
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作者：
V. Belokurov;A. Kravtsov
我们使用远地点数据版本17和GAIA早期数据版本3天体测量中对铝丰度的准确估计来选择金属丰度为−1.5≲[Fe/H]≲0.5的恒星的高纯度样本，这些恒星是在银河系中就地出生的。我们称之为极光的低金属丰度([Fe/H]≲−1.3)原位成分是运动热的，具有近似各向同性的速度椭球和适度的净旋转。极光恒星在金属度和许多元素丰度比上表现出很大的分散性。在金属丰度[Fe/H]=−1.3和−0.9之间，原位恒星的中值切向速度急剧增加，这是我们称之为自旋向上的转变。观察到的和理论上预期的年龄-金属丰度关联表明，这种增加反映了在≈1−2旋回上MW盘的快速形成。恒星运动学随[Fe/H]的变化伴随着化学丰度的质的变化：一旦银河系在[Fe/H]>；−0.9后的历元内建立了一个圆盘，散射就会急剧下降。这项研究和最近的其他研究中提出的星系形成模型的结果有力地表明，在MW中观察到的趋势反映了MW规模星系前体早期演化的一般过程：一段混乱的盘前演化时期，当气体沿着寒冷的窄丝吸积，恒星以不规则的构型诞生时，以及随后的快速盘形成。后者标志着在微波前驱星体周围形成了稳定的热气态晕，它改变了气体吸积的模式，并允许形成相干旋转的圆盘。
We use accurate estimates of aluminium abundance from the APOGEE Data Release 17 and Gaia Early Data Release 3 astrometry to select a highly pure sample of stars with metallicity −1.5 ≲ [Fe/H] ≲ 0.5 born in-situ in the Milky Way proper. The low-metallicity ([Fe/H]≲ −1.3) in-situ component we dub Aurora is kinematically hot with an approximately isotropic velocity ellipsoid and a modest net rotation. Aurora stars exhibit large scatter in metallicity and in many element abundance ratios. The median tangential velocity of the in-situ stars increases sharply with metallicity between [Fe/H]=−1.3 and −0.9, the transition that we call the spin-up. The observed and theoretically expected age-metallicity correlations imply that this increase reflects a rapid formation of the MW disk over ≈1 − 2 Gyrs. The transformation of the stellar kinematics as a function of [Fe/H] is accompanied by a qualitative change in chemical abundances: the scatter drops sharply once the Galaxy builds up a disk during later epochs corresponding to [Fe/H]>−0.9. Results of galaxy formation models presented in this and other recent studies strongly indicate that the trends observed in the MW reflect generic processes during the early evolution of progenitors of MW-sized galaxies: a period of chaotic pre-disk evolution, when gas is accreted along cold narrow filaments and when stars are born in irregular configurations, and subsequent rapid disk formation. The latter signals formation of a stable hot gaseous halo around the MW progenitor, which changes the mode of gas accretion and allows development of coherently rotating disk.