arXiv 1111.05792011-11-02astro-ph.GA

银河系内盘年轻恒星的光度距离。I. L = 314 $^{o}$方向

Photometric distances to young stars in the inner Galactic disk. I. The L = 314$^{o}$ direction

Giovanni Carraro

备注：: 23 pages, 13 eps figure, in press in Astronomy and Astrophysics
DOI：: 10.1051/0004-6361/201117238

摘要：

由于从光学到无线电的不同波长范围内的观测活动的共同努力，银河系的螺旋结构现在再次受到关注。我们在论文中开始探索银河系内部的一些关键部门，那里的螺旋结构仍然知之甚少。我们寻找可能与螺旋结构相关的年轻恒星的密度增强。为此目的，我们收集足够宽的领域UBVI测光。U波段测光的密集使用确保了红化的鲁棒性测定，从而确定光谱类型早于A0的恒星的距离，这是众所周知的旋臂示踪剂。我们使用的领域足够大，在大多数情况下都包括经过充分研究的银河系星团，我们将其作为基准来评估数据的质量和标准化，并验证我们的方法。我们在这篇文章中集中在银河经度l= 314 $^o$的视线。首先，我们进行了详尽的测试，以表明我们的数据集是在标准系统中，并校准我们的方法使用两个疏散星团NGC 5617和Pismis 19这恰好是在外地，我们发现的基本参数的估计与文献完全一致。然后，我们将该方法应用于一般领域的明星和检测签名的三个不同的群体的明星，均匀分布在整个视场，在1.5 $^{+0.5}_{-0.2}$，2.5 $^{+0.3}_{-0.5}$，和5.1 $^{+1.5}_{-1.1}$千秒差距，分别。这些距离与目前普遍接受的对船底座-人马座臂和盾牌座-十字座臂的描述是一致的，即日心距离为$\sim$ 2和5千秒差距，

英文摘要：

The spiral structure of the Milky Way is nowadays receiving renewed attention thanks to the combined efforts of observational campaigns in different wavelength regimes, from the optical to the radio. We start in the paper the exploration of a number of key sectors in the inner Milky Way, where the spiral structure is still poorly known. We search for density enhancements of young stars that might plausibly be associated with spiral structure. To this aim we collect sufficiently wide-field UBVI photometry. The intensive usage of U-band photometry ensures robust determination of reddening and hence distance for stars of spectral type earlier than A0, which are well-known spiral arm tracers. The fields we use are large enough to include in most cases well-studied Galactic clusters, which we use as bench-marks to assess the quality and standardisation of the data, and to validate our method. We focus in this paper on the line of sight to the Galactic longitude l= 314$^o$. First of all, we made exhaustive tests to show that our data-set is in the standard system, and calibrated our method using the two open clusters NGC 5617 and Pismis 19 which happen to be in the field, and for which we found estimates of the basic parameters in full agreement with the literature. We then applied the method to the general field stars and detected signatures of three different groups of stars, evenly distributed across the field of view, at 1.5$^{+0.5}_{-0.2}$, 2.5$^{+0.3}_{-0.5}$, and 5.1$^{+1.5}_{-1.1}$ kpc, respectively. These distances are compatible with the location of the nowadays commonly accepted description of the Carina-Sagittarius and Scutum-Crux arms, at heliocentric distance of $\sim$ 2 an 5 kpc,

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