Exploring the Galactic Warp through Asymmetries in the Kinematics of the Galactic Disk
Exploring the Galactic Warp through Asymmetries in the Kinematics of the Galactic Disk
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DOI：
10.3847/1538-4357/abc3c2
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
Xinlun Cheng;B. Anguiano;S. Majewski;C. Hayes;P. Arras;C. Chiappini;S. Hasselquist;Anna Bárbara de Andrade Qu
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文献类型：
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作者：
Xinlun Cheng;B. Anguiano;S. Majewski;C. Hayes;P. Arras;C. Chiappini;S. Hasselquist;Anna Bárbara de Andrade Qu
先前对银河系恒星大型数据库的分析表明，我们银河系的恒星盘是扭曲的，这给太阳附近以外的恒星的运动学提供了一个强有力的标志。然而，由于精确距离估计的限制，许多探索这些银河系特征范围的尝试通常被限制在太阳附近的体积。通过结合盖亚DR2天体测量解决方案、StarHorse距离和远地点调查的恒星丰度，我们展示了银河系盘中恒星垂直和径向运动的最详细和最广泛的研究。我们根据恒星的星系中心半径、角动量和方位角绘制恒星的速度图，并评估它们与经度的关系。在星系中心半径R = 13 kpc和角动量Lz = 2800 kpc km s−1处，发现了垂直速度的下降。在垂直和径向速度上也发现了较小的波纹叠加在主趋势上。我们还发现，垂直速度随方位角的变化趋势与峰值不对称，表明翘曲是不平衡的。为了解释垂直速度的全球趋势，我们建立了一个简单的银河系翘曲分析模型。我们的最佳拟合得到起始半径和进动速率。这些参数在不同的恒星年龄群中保持一致，这一结果支持了翘曲是外部引力引起的现象的观点。
Previous analyses of large databases of Milky Way stars have revealed the stellar disk of our Galaxy to be warped and that this imparts a strong signature on the kinematics of stars beyond the solar neighborhood. However, due to the limitation of accurate distance estimates, many attempts to explore the extent of these Galactic features have generally been restricted to a volume near the Sun. By combining the Gaia DR2 astrometric solution, StarHorse distances, and stellar abundances from the APOGEE survey, we present the most detailed and radially expansive study yet of the vertical and radial motions of stars in the Galactic disk. We map velocities of stars with respect to their Galactocentric radius, angular momentum, and azimuthal angle and assess their relation to the warp. A decrease in vertical velocity is discovered at Galactocentric radius R = 13 kpc and angular momentum Lz = 2800 kpc km s−1. Smaller ripples in vertical and radial velocity are also discovered superposed on the main trend. We also discovered that trends in the vertical velocity with azimuthal angle are not symmetric about the peak, suggesting the warp is lopsided. To explain the global trend in vertical velocity, we built a simple analytical model of the Galactic warp. Our best fit yields a starting radius of and precession rate of . These parameters remain consistent across stellar age groups, a result that supports the notion that the warp is the result of an external, gravitationally induced phenomenon.