A Galactic Plane Defined by the Milky Way H ii Region Distribution
A Galactic Plane Defined by the Milky Way H ii Region Distribution
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DOI：
10.3847/1538-4357/aaf571
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发表时间：
2018-12
期刊：
影响因子：
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通讯作者：
L. Anderson;T. Wenger;W. Armentrout;D. Balser;T. Bania
中科院分区：
文献类型：
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作者：
L. Anderson;T. Wenger;W. Armentrout;D. Balser;T. Bania
我们为银河中面的新定义开发了一个框架，允许中面相对于当前定义倾斜(；绕银河方位角90°旋转)和滚动(；绕银河方位角0°旋转)。倾斜角和滚动角的推导也确定了中面以上的太阳高度。在这里，我们使用来自星系H II区的广域红外探测星表(WISE)的星云来定义银河系高质量恒星形成(HMSF)中面。我们分析了WISE星表的各个子样本，发现它们的银河系纬度标度高度都接近0.°30，z分布标度高度接近30。小的(可能是年轻的)H II区的垂直分布比较大的(可能是老的)H II区的垂直分布窄(∼25对∼40)，这意味着较大的区域已经从它们的出生地迁移得更远。对于所有H II区子样本和各种拟合方法，我们发现HMSF中面相对于当前定义的中面没有明显的倾斜或滚动，因此，太阳接近HMSF中面。这些结果与其他对HMSF的研究一致，但与许多恒星研究不一致，可能是因为太阳附近恒星分布的不对称性。我们的结果对纬度限制和样本的完整性都很敏感，这表明对于不完整的样本，不能准确地进行类似的分析。我们开发的中面框架可以用于未来任何银河系天体的样本，以重新定义中面。
We develop a framework for a new definition of the Galactic midplane, allowing for tilt ( ; rotation about Galactic azimuth 90°) and roll ( ; rotation about Galactic azimuth 0°) of the midplane with respect to the current definition. Derivation of the tilt and roll angles also determines the solar height above the midplane. Here we use nebulae from the Wide-field Infrared Survey Explorer (WISE) Catalog of Galactic H ii Regions to define the Galactic high-mass star formation (HMSF) midplane. We analyze various subsamples of the WISE catalog and find that all have Galactic latitude scale heights near 0.°30 and z-distribution scale heights near 30 . The vertical distribution for small (presumably young) H ii regions is narrower than that of larger (presumably old) H ii regions (∼25 versus ∼40 ), implying that the larger regions have migrated further from their birth sites. For all H ii region subsamples and for a variety of fitting methodologies, we find that the HMSF midplane is not significantly tilted or rolled with respect to the currently defined midplane, and, therefore, the Sun is near to the HMSF midplane. These results are consistent with other studies of HMSF, but are inconsistent with many stellar studies, perhaps because of asymmetries in the stellar distribution near the Sun. Our results are sensitive to latitude restrictions and also to the completeness of the sample, indicating that similar analyses cannot be done accurately with less complete samples. The midplane framework we develop can be used for any future sample of Galactic objects to redefine the midplane.