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arXiv 0902.3403astro-ph.GA
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分子云的结构:I -全天近红外消光图

The Structure of Molecular Clouds: I - All Sky Near Infrared Extinction Maps

J. Rowles, D. Froebrich

摘要:

我们正在研究附近所有巨大分子云的柱密度分布。作为这个项目的一部分,我们生成了几个全天空灭绝地图。它们是使用中值近红外颜色过量技术计算的,该技术应用于2微米全天巡天(2 MASS)的数据。我们的大规模方法使我们能够将样条函数拟合到无消光区域,以便准确确定颜色过量值。两种类型的地图:一)地图与恒定的噪音和可变的空间分辨率;二)地图与恒定的空间分辨率和可变的噪音。我们的标准Av图使用距离每个像素中心最近的49颗恒星来确定灭绝。在整个地图中,一西格玛方差恒定在0.28 mag Av。到第49颗最近恒星的距离从银道面附近的1arcmin到两极的10arcmin不等,但对于所有巨大的分子云(|b| <30度)来说都在5arcmin以下。与现有的大比例尺地图的比较表明,我们的消光值比Dobashi等人的大20%,比Schlegel等人的小40%。这很可能是由Dobashi等人应用的恒星计数技术和Schlegel等人尘埃温度和发射率的系统不确定性造成的。与其他两张地图相比,我们卓越的分辨率使我们能够检测到更多的小规模高消光核心。

英文摘要:

We are studying the column density distribution of all nearby giant molecular clouds. As part of this project we generated several all sky extinction maps. They are calculated using the median near infrared colour excess technique applied to data from the Two Micron All-Sky Survey (2MASS). Our large scale approach allows us to fit spline functions to extinction free regions in order to accurately determine the colour excess values. Two types of maps are presented: i) Maps with a constant noise and variable spatial resolution; ii) Maps with a constant spatial resolution and variable noise. Our standard Av map uses the nearest 49 stars to the centre of each pixel for the determination of the extinction. The one sigma variance is constant at 0.28mag Av in the entire map. The distance to the 49th nearest star varies from below 1arcmin near the Galactic Plane to about 10arcmin at the poles, but is below 5arcmin for all giant molecular clouds (|b|< 30degr). A comparison with existing large scale maps shows that our extinction values are systematically larger by 20% compared to Dobashi et al. and 40% smaller compared to Schlegel et al.. This is most likely caused by the applied star counting technique in Dobashi et al. and systematic uncertainties in the dust temperature and emissivity in Schlegel et al.. Our superior resolution allows us to detect more small scale high extinction cores compared to the other two maps.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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