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arXiv 2106.04529astro-ph.GA
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沿银河中心视线到Milky Way旋臂的距离和消光

Distance and extinction to the Milky Way spiral arms along the Galactic centre line of sight

Francisco Nogueras-Lara, Rainer Schödel, Nadine Neumayer

备注：
Updated to the final version accepted for publication in Astronomy & Astrophysics. 17 pages, 12 figures
发表信息：
A&A 653, A33 (2021)
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摘要：

太阳在银河系盘内的位置阻碍了对旋臂结构的研究。我们的目标是分析沿着银河系中心（GC）的视线的旋臂，以确定它们的距离，灭绝和恒星人口。我们使用GALACTICNUCLEUS巡天，这是一个JHK的高角分辨率测光星表（0.2”），用于银河系的最内部区域。我们通过$χ^2$最小化将简单的合成颜色-星等模型拟合到我们的数据中。我们计算了探测到的旋臂的距离和消光。我们还分析了消光曲线和检测到的功能之间的相对消光。最后，我们建立了修正后的Ks光度函数（KLF）来研究第二和第三旋臂特征中存在的恒星种群。我们确定了到旋臂的平均距离：$d1=1.6\pm0.2$、$d2=2.6\pm0.2$、$d3=3.9\pm0.3$和$d4=4.5\pm0.2$ kpc，以及平均距离：$A_{H1}=0.35\pm0.08$、$A_{H2}=0.77\pm0.08$、$A_{H3}=1.68\pm0.08$和$A_{H4}=2.30\pm0.08$ ma。我们分析了旋臂中恒星的近红外消光曲线，发现了$A_J/A_{H}=1.89\pm0.11$和$A_H/A_{K_s}=1.86\pm0.11$的平均值，与GC获得的结果一致。这意味着消光曲线的形状不依赖于距离或绝对消光。我们还为每个旋臂建立了消光图，并得出它们是均匀的，可能对应于独立的消光层。最后，通过分析第二和第三旋臂的KLF，我们发现它们具有相似的恒星种群。我们获得了两个主要的恒星形成事件：$>6$ Gyr（恒星质量的$\sim60-70\%$）和$1.5-4$ Gyr（恒星质量的$\sim20-30\%$），与以前的工作兼容。我们还检测到最近的恒星形成在一个较低的水平（$\sim10\%$）的第三个螺旋臂。

英文摘要：

The position of the Sun inside the Milky Way's disc hampers the study of the spiral arm structure. We aim to analyse the spiral arms along the line-of-sight towards the Galactic centre (GC) to determine their distance, extinction, and stellar population. We use the GALACTICNUCLEUS survey, a JHKs high angular resolution photometric catalogue (0.2") for the innermost regions of the Galaxy. We fitted simple synthetic colour-magnitude models to our data via $χ^2$ minimisation. We computed the distance and extinction to the detected spiral arms. We also analysed the extinction curve and the relative extinction between the detected features. Finally, we built extinction-corrected Ks luminosity functions (KLFs) to study the stellar populations present in the second and third spiral arm features. We determined the mean distances to the spiral arms: $d1=1.6\pm0.2$, $d2=2.6\pm0.2$, $d3=3.9\pm0.3$, and $d4=4.5\pm0.2$ kpc, and the mean extinctions: $A_{H1}=0.35\pm0.08$, $A_{H2}=0.77\pm0.08$, $A_{H3}=1.68\pm0.08$, and $A_{H4}=2.30\pm0.08$ mag. We analysed the extinction curve in the near infrared for the stars in the spiral arms and found mean values of $A_J/A_{H}=1.89\pm0.11$ and $A_H/A_{K_s}=1.86\pm0.11$, in agreement with the results obtained for the GC. This implies that the shape of the extinction curve does not depend on distance or absolute extinction. We also built extinction maps for each spiral arm and obtained that they are homogeneous and might correspond to independent extinction layers. Finally, analysing the KLFs from the second and the third spiral arms, we found that they have similar stellar populations. We obtained two main episodes of star formation: $>6$ Gyr ($\sim60-70\%$ of the stellar mass), and $1.5-4$ Gyr ($\sim20-30\%$ of the stellar mass), compatible with previous work. We also detected recent star formation at a lower level ($\sim10\%$) for the third spiral arm.

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