Galactic Cold Interstellar Filaments: Structure, Kinematics, and Chemistry

众所周知，分子星际介质具有高度的层次性和丝状结构。近年来的研究已经证明了细丝在恒星形成中的重要性，其尺度为&lt；10pC和&gt；100pC，并提出了恒星形成的新范式。然而，在10-100pC尺度上的极端丝状巨型分子云(GMC)还没有得到系统的研究。由于鉴定方法的历史限制(即灭绝)，最初并不存在令人信服的样本。在这个项目中，我们使用完整的Hi-GAL图像来直接在整个银河系平面上寻找大的暗条。我们选择了9个最突出的细丝样本，其长度为30-103pC，质量为(2.4-19)x10^4mSun。与周围环境相比，灯丝是冷的，没有明显的内部加热。这使得我们的项目在探索早期进化阶段以研究丝状GMCs与恒星形成的开始之间的联系方面是独一无二的。我们建议首先对这些细丝进行系统的表征，重点放在它们的等级结构、运动学和核心化学上，目的是揭示在大细丝背景下高质量恒星形成的全面图景。这些方法的设计使得结果可以直接与数值模拟和理论预测相比较。这是一个及时的项目，利用最新的Hi-GAL数据，将填补银河系和地方性细丝之间的空白，朝着在所有空间尺度上理解细丝的方向迈进。

Molecular interstellar medium is known to be highly hierarchical and filamentary. Studies in recent years have demonstrated the importance of filaments in star formation, at scales of <10 pc and >100 pc, and suggest a new paradigm for star formation. However, extremely filamentary giant molecular clouds (GMCs) at scales between 10 and 100 pc have not been studied systematically. A compelling sample does not exist at the first place, due to a historical limitation in the identifying methodology (i.e., extinction). In this project, we use the full Hi-GAL images to directly search for large filaments in the entire Galactic plane. We select a sample of 9 most prominent filaments with a length of 30-103 pc and mass (2.4-19)x10^4 Msun. The filaments are cold compared to surroundings and show no significant internal heating. This makes our project unique in probing the early evolutionary phases to study the connection of filamentary GMCs to the onset of star formation. We propose to perform a first systematic characterization of these filaments focusing on their hierarchical structure, kinematics, and core chemistry, aiming to reveal a comprehensive picture of high-mass star formation in the context of large filaments. The methods are designed so that results are directly comparable to numerical simulations and theoretical predictions. This is a timely project making use of the newly available Hi-GAL data, and will fill the gap between Galactic and local filaments, towards an understanding of filaments at all spatial scales.