论文标题
H3调查显示的银河盘的诞生
Birth of the Galactic Disk Revealed by the H3 Survey
论文作者
论文摘要
我们使用化学（[alpha/fe]和[Fe/h]），主要序列转弯年龄以及从H3调查光谱和GAIA天文学确定的运动学来鉴定银河系磁盘的出生。我们基于角动量和偏心率将原位和积聚的恒星分开。高α高静脉恒星的序列持续至至少[Fe/H] = -2.5，显示出意外的非单调行为：随着金属性的增加，人口首先下降[alpha/fe]，然后在-1.3 <[fe/h] <-0.7范围内增加，然后在较高的金属金属上再次下降。原位种群中的恒星数量迅速增加了[Fe/H] = -1。这些恒星的平均运动学在[fe/h] <-1时与金属性无关，然后在较高的金属度下变得越来越冷且磁盘样。位于原位的高α恒星的年龄在[fe/h] <-1.3处均匀陈年（13 Gyr），并在较高的金属度上跨越较大的范围（8-12 Gyr）。用简单的化学进化模型解释化学，表明非单调行为是由于恒星形成效率显着提高，该恒星形成效率始于13 GYR。这些结果支持一张图片，其中的第一个1 Gyr的星系为特征，其特征是“缩小阶段”，其中恒星形成效率较低，并且运动学具有实质性疾病，并具有一定的净旋转。然后，磁盘对“沸腾阶段”进行了戏剧性的转化，其中恒星形成效率大大提高，运动学变为磁盘状，而恒星的数量则增加了十倍。我们将这种转换解释为在Z〜4处的银河盘的诞生。这种转换的物理起源尚不清楚，并且似乎在当前的星系形成模型中并未再现。
We use chemistry ([alpha/Fe] and [Fe/H]), main sequence turnoff ages, and kinematics determined from H3 Survey spectroscopy and Gaia astrometry to identify the birth of the Galactic disk. We separate in-situ and accreted stars on the basis of angular momenta and eccentricities. The sequence of high-alpha in-situ stars persists down to at least [Fe/H]=-2.5 and shows unexpected non-monotonic behavior: with increasing metallicity the population first declines in [alpha/Fe], then increases over the range -1.3<[Fe/H]<-0.7, and then declines again at higher metallicities. The number of stars in the in-situ population rapidly increases above [Fe/H]=-1. The average kinematics of these stars are hot and independent of metallicity at [Fe/H]<-1 and then become increasingly cold and disk-like at higher metallicities. The ages of the in-situ, high-alpha stars are uniformly very old (13 Gyr) at [Fe/H]<-1.3, and span a wider range (8-12 Gyr) at higher metallicities. Interpreting the chemistry with a simple chemical evolution model suggests that the non-monotonic behavior is due to a significant increase in star formation efficiency, which began 13 Gyr ago. These results support a picture in which the first 1 Gyr of the Galaxy was characterized by a "simmering phase" in which the star formation efficiency was low and the kinematics had substantial disorder with some net rotation. The disk then underwent a dramatic transformation to a "boiling phase", in which the star formation efficiency increased substantially, the kinematics became disk-like, and the number of stars formed increased tenfold. We interpret this transformation as the birth of the Galactic disk at z~4. The physical origin of this transformation is unclear and does not seem to be reproduced in current galaxy formation models.
