寻找外银道面I中的暗云--识别2 MASS中扩展红区的统计方法
Searching for dark clouds in the outer galactic plane I -- A statistical approach for identifying extended red(dened) regions in 2MASS
摘要：
虽然红外暗云在形成过程中的确切作用仍然不清楚，但它们似乎为研究星团形成的早期阶段提供了有用的实验室。红外暗云主要是朝向银道面明亮的内部。低背景发射使得在外部的中红外吸收中识别类似物体更加困难。这是不幸的，因为外星系是我们可以研究不同（外部）条件对恒星形成过程影响的唯一附近区域。本文的目的是确定扩展的红色区域在银河系外平面的基础上，在近红外的恒星红化。我们认为，这些地区出现红色主要是由于分子云和年轻的恒星物体造成的灭绝。这里介绍的工作是用来作为识别恒星形成区域，特别是非常早期阶段的基础。我们使用曼-惠特尼U-检验，结合朋友的朋友算法，以确定扩展的红色区域在2 MASS全天空JHK调查。我们使用60”和90”两种不同的分辨率在规则网格上处理数据。之所以选择这两种分辨率，是因为恒星表面密度在拥挤的旋臂区域和人口稀少的银河系反中心区域之间变化。我们确定1320扩展红色区域在较高的分辨率和1589在较低的分辨率运行。大多数区域与主要的分子云复合体有关，支持我们的假设，即变红主要是由于前景云和嵌入的物体。
英文摘要：
[Abridged] Though the exact role of infrared dark clouds in the formation process is still somewhat unclear, they seem to provide useful laboratories to study the very early stages of clustered star formation. Infrared dark clouds have been identified predominantly toward the bright inner parts of the galactic plane. The low background emission makes it more difficult to identify similar objects in mid-infrared absorption in the outer parts. This is unfortunate, because the outer Galaxy represents the only nearby region where we can study effects of different (external) conditions on the star formation process. The aim of this paper is to identify extended red regions in the outer galactic plane based on reddening of stars in the near-infrared. We argue that these regions appear reddened mainly due to extinction caused by molecular clouds and young stellar objects. The work presented here is used as a basis for identifying star forming regions and in particular the very early stages. We use the Mann-Whitney U-test, in combination with a friends-of-friends algorithm, to identify extended reddened regions in the 2MASS all-sky JHK survey. We process the data on a regular grid using two different resolutions, 60" and 90". The two resolutions have been chosen because the stellar surface density varies between the crowded spiral arm regions and the sparsely populated galactic anti-center region. We identify 1320 extended red regions at the higher resolution and 1589 at the lower resolution run. The majority of regions are associated with major molecular cloud complexes, supporting our hypothesis that the reddening is mostly due to foreground clouds and embedded objects.
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