arXiv 0906.34932009-06-18astro-ph.GA

恒星原星团形成的初始条件。I.斯皮策星云的目录

The initial conditions of stellar protocluster formation. I. A catalogue of Spitzer dark clouds

N. Peretto, G. A. Fuller

备注：: 12 pages, 12 figures, accepted for publication in A&A
DOI：: 10.1051/0004-6361/200912127

摘要：

大多数恒星形成于星团中。因此，全面了解恒星形成需要了解团簇形成的初始条件。我们的研究目标是阐明红外暗云（IRDC）的物理性质及其在星团形成中的作用。这篇文章是专门研究IRDC的系列文章的第一篇，描述了为建立银河系斯皮策IRDC的完整目录而开发的技术。我们分析了斯皮策GLIMPSE和MIPSGAL的数据，以确定银河经度和纬度10度< |l| <65度和|b| <1deg. From the 8micron observations we have constructed opacity maps and used a newly developed extraction algorithm to identify structures above a column density of N_{H2} >1 × 10 ^{22} cm^{-2}区域内的IRDC的完整样本。24微米的数据然后被用来表征每个提取的云的恒星形成活动。总共提取了11303个云。与现有的基于MSX的IRDC目录相比，这些斯皮策星云中有80%以前是未知的。该算法还提取这些云内的~ 20000至50000片段，这取决于所使用的检测阈值。MIPSGAL的数据表明，这些IRDC中有20%到68%显示出24微米的点状关联。这个新的数据库为未来的研究提供了重要的资源，旨在了解银河系恒星形成的初始条件。

英文摘要：

The majority of stars form in clusters. Therefore a comprehensive view of star formation requires understanding the initial conditions for cluster formation. The goal of our study is to shed light on the physical properties of infrared dark clouds (IRDCs) and the role they play in the formation of stellar clusters. This article, the first of a series dedicated to the study of IRDCs, describes techniques developed to establish a complete catalogue of Spitzer IRDCs in the Galaxy. We have analysed Spitzer GLIMPSE and MIPSGAL data to identify a complete sample of IRDCs in the region of Galactic longitude and latitude 10deg < |l|<65deg and |b|<1deg. From the 8micron observations we have constructed opacity maps and used a newly developed extraction algorithm to identify structures above a column density of N_{H2} > 1x10^{22} cm^{-2}. The 24micron data are then used to characterize the star formation activity of each extracted cloud. A total of 11303 clouds have been extracted. A comparison with the existing MSX based catalogue of IRDCs shows that 80% of these Spitzer dark clouds were previously unknown. The algorithm also extracts ~ 20000 to 50000 fragments within these clouds, depending on detection threshold used. A first look at the MIPSGAL data indicates that between 20% and 68% of these IRDCs show 24micron point-like association. This new database provides an important resource for future studies aiming to understand the initial conditions of star formation in the Galaxy.

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