STRUCTURE AND KINEMATICS OF THE STELLAR HALOS AND THICK DISKS OF THE MILKY WAY BASED ON CALIBRATION STARS FROM SLOAN DIGITAL SKY SURVEY DR7
STRUCTURE AND KINEMATICS OF THE STELLAR HALOS AND THICK DISKS OF THE MILKY WAY BASED ON CALIBRATION STARS FROM SLOAN DIGITAL SKY SURVEY DR7
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DOI：
10.1088/0004-637x/712/1/692
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发表时间：
2009-09
期刊：
影响因子：
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通讯作者：
D. Carollo;T. Beers;M. Chiba;J. Norris;K. Freeman;Y. S. Lee;Ž. Ivezić;C. Rockosi;B. Yanny
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文献类型：
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作者：
D. Carollo;T. Beers;M. Chiba;J. Norris;K. Freeman;Y. S. Lee;Ž. Ivezić;C. Rockosi;B. Yanny
基于斯隆数字巡天 (SDSS) 及其第一个扩展 SDSS-II（其中包括子巡天斯隆银河理解与探索扩展 (SEGUE)）中 32360 颗“校准星”的明确大气参数和运动学量，探索了银河系公认恒星组成部分的结构和运动学。 16,920 颗恒星的子样本的全空间运动，探索太阳 4 kpc 以内的局部体积，用于导出银河系内晕和外晕组成部分的速度椭球体，以及规范厚盘和拟议的金属弱厚盘 (MWTD) 群。这个新的校准星样本比之前分析中使用的数量增加了 60%。我们首先检查数据是否需要至少存在两个分量的光晕，以便解释局部体积中可能的光晕恒星的旋转行为，以及是否需要两个以上的分量。我们还解决了所提出的 MWTD 在运动学和化学上是否与典型厚盘不同的问题，并指出为 MWTD 推断的银河中心旋转速度及其平均金属丰度，似乎与之前针对麒麟座流得出的值非常相似，表明这些结构之间可能存在关联。此外，我们还考虑了理解所观察到的银河系恒星群运动学行为的性质所需的每个成分的分数，作为距平面距离的函数。确定厚盘和 MWTD 组件的标尺长度和标尺高度。内晕和外晕群体的空间密度分布是根据金斯定理分析推断出来的。全套校准恒星（包括局部体积之外的恒星）用于测试观测到的恒星金属丰度分布函数随银河平面上方距离的预期变化，这是由于底层恒星种群的贡献变化所致。根据现代冷暗物质星系形成模型，结合其他类银河系的理论和观测约束，考虑上述问题。
The structure and kinematics of the recognized stellar components of the Milky Way are explored, based on well-determined atmospheric parameters and kinematic quantities for 32360 “calibration stars” from the Sloan Digital Sky Survey (SDSS) and its first extension, SDSS-II, which included the sub-survey Sloan Extension for Galactic Understanding and Exploration (SEGUE). Full space motions for a sub-sample of 16,920 stars, exploring a local volume within 4 kpc of the Sun, are used to derive velocity ellipsoids for the inner- and outer-halo components of the Galaxy, as well as for the canonical thick-disk and proposed metal-weak thick-disk (MWTD) populations. This new sample of calibration stars represents an increase of 60% relative to the numbers used in a previous analysis. We first examine the question of whether the data require the presence of at least a two-component halo in order to account for the rotational behavior of likely halo stars in the local volume, and whether more than two components are needed. We also address the question of whether the proposed MWTD is kinematically and chemically distinct from the canonical thick disk, and point out that the Galactocentric rotational velocity inferred for the MWTD, as well as its mean metallicity, appear quite similar to the values derived previously for the Monoceros stream, suggesting a possible association between these structures. In addition, we consider the fractions of each component required to understand the nature of the observed kinematic behavior of the stellar populations of the Galaxy as a function of distance from the plane. Scale lengths and scale heights for the thick-disk and MWTD components are determined. Spatial density profiles for the inner- and outer-halo populations are inferred from a Jeans theorem analysis. The full set of calibration stars (including those outside the local volume) is used to test for the expected changes in the observed stellar metallicity distribution function with distance above the Galactic plane in situ, due to the changing contributions from the underlying stellar populations. The above issues are considered, in concert with theoretical and observational constraints from other Milky-Way-like galaxies, in light of modern cold dark matter galaxy formation models.