The structure of the Milky Way's bar outside the bulge
The structure of the Milky Way's bar outside the bulge
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DOI：
10.1093/mnras/stv745
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发表时间：
2015-04
影响因子：
4.8
通讯作者：
C. Wegg;O. Gerhard;Matthieu Portail
中科院分区：
文献类型：
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作者：
C. Wegg;O. Gerhard;Matthieu Portail
虽然银河系内部确实存在一个棒，但其靠近银道面的结构仍不确定，那里因尘埃的介入而造成的灭绝最为严重。我们在这里使用来自 UKIDSS、2MASS、VVV 和 GLIMPSE 的红丛巨星 (RCG) 来研究核球外的银条，即长条。我们匹配并组合这些调查，以调查纬度和经度 |b|<9deg 和 |l|<40deg 的广阔区域。我们发现： (1) 棒在距银道面 |b|~5deg 处延伸至 l~25deg，在低纬度处延伸至 l~30deg。 (2) 长条与视线的角度在 (28-33) 度范围内，与 |l|<10 度处的凸起研究一致。 (3) RCG星体的尺度高度从凸起到较细的长条平滑过渡。 (4) 有证据表明长条中有两个刻度高度。我们发现了一个约 180pc 的细棒组件，让人想起太阳附近的旧薄圆盘，以及一个约 45pc 的超细棒组件，主要存在于棒端。 (5) 构建 RC 幅度分布的参数模型，我们发现 2 分量棒的棒半长度为 5.0+-0.2kpc，单独的细棒分量为 4.6+-0.3kpc。我们得出的结论是，银河系包含一个中心盒/花生核，它是一个更长、更平坦的棒的垂直延伸，与外部星系和 N 体模型中看到的类似。
While it is incontrovertible that the inner Galaxy contains a bar, its structure near the Galactic plane has remained uncertain, where extinction from intervening dust is greatest. We investigate here the Galactic bar outside the bulge, the long bar, using red clump giant (RCG) stars from UKIDSS, 2MASS, VVV, and GLIMPSE. We match and combine these surveys to investigate a wide area in latitude and longitude, |b|<9deg and |l|<40deg. We find: (1) The bar extends to l~25deg at |b|~5deg from the Galactic plane, and to l~30deg at lower latitudes. (2) The long bar has an angle to the line-of-sight in the range (28-33)deg, consistent with studies of the bulge at |l|<10deg. (3) The scale-height of RCG stars smoothly transitions from the bulge to the thinner long bar. (4) There is evidence for two scale heights in the long bar. We find a ~180pc thin bar component reminiscent of the old thin disk near the sun, and a ~45pc super-thin bar component which exists predominantly towards the bar end. (5) Constructing parametric models for the RC magnitude distributions, we find a bar half length of 5.0+-0.2kpc for the 2-component bar, and 4.6+-0.3kpc for the thin bar component alone. We conclude that the Milky Way contains a central box/peanut bulge which is the vertical extension of a longer, flatter bar, similar as seen in both external galaxies and N-body models.