Angular Momentum Variation of the Milky Way Thick Disk: The Dependence of Chemical Abundance and Evidence of the Inside-out Formation Scenario
Angular Momentum Variation of the Milky Way Thick Disk: The Dependence of Chemical Abundance and Evidence of the Inside-out Formation Scenario
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DOI：
10.3847/1538-4357/acd058
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发表时间：
2023-06
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通讯作者：
Guozhen 国真 Hu 胡;Zhengyi 正义 Shao 邵;Lu 璐 Li 李
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作者：
Guozhen 国真 Hu 胡;Zhengyi 正义 Shao 邵;Lu 璐 Li 李
我们使用APOGEE数据发布（DR）17和盖亚早期DR 3的26，076颗巨星样本研究了银河系厚盘单丰度种群（MAP）的角动量。在[α/M]-[M/H]平面上，窄仓内MAP的垂直和垂直角动量分量LZ和LP具有显著的变化。L Z和L P随[M/H]和[α/M]系统地变化，并且可以通过化学梯度进行定量：d[M/H]/dL Z = 1.2 × 10−3 dex kpc−1 km−1 s，d[M/H]/dL P = −5.0 × 10−3 dex kpc−1 km−1 s，d[α/M]/dL Z = −3.0 × 10−4 dex kpc−1 km−1 s，d[α/M]/dL P = 1.2 × 10 - 3 dec kpc-1 km-1 s。这些相关性也可以解释为MAPs空间分布形状的化学依赖性。我们还展示了相应的角动量分量的年龄依赖性。在引导半径（R g）与LZ成正比的假设下，这提供了厚盘由内而外结构形成的直接观测证据，dR g /dAge = −1.9 kpc Gyr−1。圆盘厚度的逐渐变化可以用倒置形成或/和随后的运动学加热来解释。
We investigate the angular momentum of mono-abundance populations (MAPs) of the Milky Way thick disk by using a sample of 26,076 giant stars taken from APOGEE Data Release (DR) 17 and Gaia early DR3. The vertical and perpendicular angular momentum components, L Z and L P , of the MAPs in narrow bins have significant variations across the [α/M]–[M/H] plane. L Z and L P systematically change with [M/H] and [α/M] and can be alternatively quantified by the chemical gradients: d[M/H]/dL Z = 1.2 × 10−3 dex kpc−1 km−1 s, d[M/H]/dL P = −5.0 × 10−3 dec kpc−1 km−1 s, and d[α/M]/dL Z = −3.0 × 10−4 dex kpc−1 km−1 s, d[α/M]/dL P = 1.2 × 10−3 dec kpc−1 km−1 s. These correlations can also be explained as the chemical dependence of the spatial distribution shape of the MAPs. We also exhibit the corresponding age dependence of the angular momentum components. Under the assumption that the guiding radius (R g ) is proportional to L Z , this provides direct observational evidence of the inside-out structure formation scenario of the thick disk, with dR g /dAge = −1.9 kpc Gyr−1. The progressive changes in the disk thickness can be explained by the upside-down formation or/and the consequent kinematical heating.