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arXiv 1405.7003astro-ph.GA
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从CGPS看外Milky Way的螺旋结构I:到恒星形成区的距离和速度

A CGPS Look at the Spiral Structure of the Outer Milky Way I: Distances and Velocities to Star Forming Regions

Tyler J. Foster, Christopher M. Brunt

摘要:

我们提出了一个新的目录的分光光度计的距离和视线系统速度之间的90 $^{\circ}\leq \ell \leq~$ 195 $^{\circ}$(经度象限II和III的一部分)103 HII地区。利用1角分分辨率的21 cm HI和2.6 mm $^{12}$ CO线图(来自加拿大银道面巡天和FCRAO外星系巡天),分别测量了每个区域的两个新速度。将已知的和邻近的具有UBV光度学和MK分类的OB型恒星叠加到21厘米连续谱图上,用在HII辐射边界内的恒星(其距离不超过其他恒星的3倍标准差)计算了新的平均恒星到103个星云的距离。使用这种方法排除距离异常值的平均距离,一组许多恒星在每个HII区域减少了异常变红的影响,为某些个人。9个常见天体的最终平均距离与VLBI视差距离呈1:1的对应关系。此外,与这些象限中的HII区域的先前目录相比,在同一区域中到英仙座旋臂物体的距离的散射减少了50%,并且在相对于太阳的共同角速度$Ω-Ω_0$(km~s $^{-1}$ ~kpc $^{-1}$)周围的散射减少了$\sim$ 1/ $\sqrt{2}$。该星表的目的是为在2 $^{\textrm{nd}}$和3 $^{\textrm{rd}}$象限进行更详细的大尺度银河螺旋结构和动力学(旋转曲线、密度波流)研究奠定基础,这两个象限从太阳的位置看是银河系中最有利的部分。

英文摘要:

We present a new catalogue of spectrophotometric distances and line-of-sight systemic velocities to 103 HII regions between 90$^{\circ}\leq \ell \leq~$195$^{\circ}$ (longitude quadrants II and part of III). Two new velocities for each region are independently measured using 1-arcminute resolution 21~cm HI and 2.6~mm $^{12}$CO line maps (from the Canadian Galactic Plane Survey and FCRAO Outer Galaxy Surveys) that show where gaseous shells are observed around the periphery of the ionized gas. Known and neighbouring OB-type stars with published UBV photometry and MK classifications are overlaid onto 21~cm continuum maps, and those stars observed within the boundary of the HII emission (and whose distance is not more than 3 times the standard deviation of the others) are used to calculate new mean stellar distances to each of the 103 nebulae. Using this approach of excluding distance outliers from the mean distance to a group of many stars in each HII region lessens the impact of anomalous reddening for certain individuals. Final mean distances of 9 common objects with VLBI parallax distances show a 1:1 correspondence. Further, comparison with previous catalogues of HII regions in these quadrants shows a 50% reduction in scatter for the distance to Perseus spiral arm objects in the same region, and a reduction by $\sim$1/$\sqrt{2}$ in scatter around a common angular velocity relative to the Sun $Ω-Ω_0$(km~s$^{-1}$~kpc$^{-1}$). The purpose of the catalogue is to provide a foundation for more detailed large-scale Galactic spiral structure and dynamics (rotation curve, density wave streaming) studies in the 2$^{\textrm{nd}}$ and 3$^{\textrm{rd}}$ quadrants, which from the Sun's location is the most favourably viewed section of the Galaxy.

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