论文标题
银河系的外部螺旋臂使用红色团星
The Outer spiral arm of the Milky Way using Red Clump stars
论文作者
论文摘要
目的：我们的目的是使用红色团恒星的分布来提供银河系的旧光盘结构的观察视图。圆盘中存在的螺旋臂，翘曲结构和其他不对称性通过对星系盘上的红色团恒星计数进行系统的研究进行了重新访问。 方法：我们开发了一种方法来系统地从2粒（$ j-k_s，〜j $）颜色图中提取红色团星，$ 1^\ circ \ circ \ circ \ circ \ circ \ circ $ bin $ \ ell \ ell \ ell \ times b $覆盖范围$ 40^\ circ \ le 320^le 320^circ $ $ -10^circ $ $ -10^circ $ -10^ly croct ucd^le crocc ly circ $ $ -10^^ly crouck和circ。 2个弹药数据仍然很重要，因为它能够识别并追踪红色恒星的距离要比任何光盘的任何光学调查更远。通过利用GAIA EDR3的精确星形数据去除所选样品中的前景星污染。 结果：我们已经生成了星系的面对面（XY平面），描绘了银河平面上方和下方的密度分布和计数比。所得的红色团星的过度密度从第二个象限到第三个银河象限的外臂的连续形态。这是第一个使用红色团恒星绘制外臂在圆盘上绘制外臂的研究。通过这项研究，我们能够首次将外臂井到第三个银河象限中。除了螺旋结构外，我们还看到了在银河平面上方和下方的波浪状的不对称性，相对于指示翘曲结构的纵向。通过追踪银河平面上方和下方的红色块恒星的比率来系统地研究经线结构。我们提供了外部螺旋臂中不对称性的第一个直接观察证据，证实了老年人群所追踪的螺旋臂也被扭曲，类似于椎间盘。
Aims: Our aim is to provide an observational view of the old Disc structure of the Milky Way galaxy using the distribution of red clump stars. The spiral arms, warp structure, and other asymmetries present in the Disc are re-visited using a systematic study of red clump star counts over the disc of the Galaxy. Methods: We developed a method to systematically extract the red clump stars from 2MASS ($J-K_s, ~J$) colour-magnitude diagram of $1^\circ \times 1^\circ$ bins in $\ell \times b$ covering the range $40^\circ \le \ell \le 320^\circ$ and $-10^\circ \le b \le 10^\circ$. 2MASS data continues to be important since it is able to identify and trace the red clump stars to much farther distances than any optical survey of the Disc. The foreground star contamination in the selected sample is removed by utilising the accurate astrometric data from Gaia EDR3. Results: We have generated a face-on-view (XY-plane) of the Galaxy depicting the density distribution and count ratio above and below the Galactic plane. The resulting over-density of red clump stars traces the continuous morphology of the Outer arm from the second to the third Galactic quadrant. This is the first study to map the Outer arms across the disc using red clump stars. Through this study, we are able to trace the Outer arm well into the 3rd Galactic quadrant for the first time. Apart from the spiral structures, we also see a wave-like asymmetry above and below the Galactic plane with respect to longitudes indicating the warp structure. The warp structure is studied systematically by tracing the ratio of red clump stars above and below the Galactic plane. We provide the first direct observational evidence of the asymmetry in the Outer spiral arms confirming that the spiral arms traced by the older population are also warped, similar to the Disc.
