MAPPING THE ASYMMETRIC THICK DISK. III. THE KINEMATICS AND INTERACTION WITH THE GALACTIC BAR
MAPPING THE ASYMMETRIC THICK DISK. III. THE KINEMATICS AND INTERACTION WITH THE GALACTIC BAR
复制标题
绘制不对称厚盘。
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
J. Larsen
中科院分区：
文献类型：
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作者：
R. Humphreys;T. Beers;J. E. Cabanela;S. Grammer;K. Davidson;Y. S. Lee;J. Larsen
在本系列的前两篇论文中，Larsen 等人。描述我们在银河系内部的微弱 CCD 调查，并将象限 1 (Q1) 中厚盘恒星的超密度沿视线绘制到 5 kpc 或更多。显示出最强过剩的区域位于银盘中条形密度等值线上方。在关于不对称厚盘的第三篇论文中，我们报告了 Q1、平面上方和下方以及平面上方第四象限 (Q4) 中 4000 多颗恒星的径向速度和导出的金属丰度参数。我们证实了 Parker 等人首先报道的相应运动不对称性，并扩展到更远的距离和更大的空间覆盖范围。 Q1中的厚盘星相对于圆周自转有60-70 km s−1的旋转滞后，而弱金属厚盘星的滞后甚至更大，为100 km s−1。两者都落后于 Q4 中相应的种群约 30 km s−1。有趣的是，Q1 中的盘状恒星似乎也参与了大约 30 km s−1 的旋转滞后。 Q1 中厚盘的增强旋转滞后从太阳延伸到 4 kpc 或更多。在 3-4 kpc 时，我们的视线延伸到条形图近侧的密度等值线之上，并且当我们的视线直接穿过条形图时，旋转滞后似乎会减少。这与圆盘中旋转杆引起的“引力尾流”一致，该尾流会将恒星捕获并堆积在其后面。我们的结论是，与恒星棒的动态相互作用是观察到的运动学和空间不对称性的最可能的解释。
In the first two papers of this series, Larsen et al. describe our faint CCD survey in the inner Galaxy and map the overdensity of thick disk stars in Quadrant 1 (Q1) to 5 kpc or more along the line of sight. The regions showing the strongest excess are above the density contours of the bar in the Galactic disk. In this third paper on the asymmetric thick disk, we report on radial velocities and derived metallicity parameters for over 4000 stars in Q1, above and below the plane, and in Quadrant 4 (Q4) above the plane. We confirm the corresponding kinematic asymmetry first reported by Parker et al., extended to greater distances and with more spatial coverage. The thick disk stars in Q1 have a rotational lag of 60–70 km s−1 relative to circular rotation, and the metal-weak thick disk stars have an even greater lag of 100 km s−1. Both lag their corresponding populations in Q4 by ≈30 km s−1. Interestingly, the disk stars in Q1 also appear to participate in the rotational lag by about 30 km s−1. The enhanced rotational lag for the thick disk in Q1 extends to 4 kpc or more from the Sun. At 3–4 kpc, our sight lines extend above the density contours on the near side of the bar, and as our lines of sight pass directly over the bar the rotational lag appears to decrease. This is consistent with a “gravitational wake” induced by the rotating bar in the disk which would trap and pile up stars behind it. We conclude that a dynamical interaction with the stellar bar is the most probable explanation for the observed kinematic and spatial asymmetries.