Large-scale filaments associated with Milky Way spiral arms

Abstract

The ubiquity of filamentary structure at various scales through out the Galaxy has triggered a renewed interest in their formation, evolution, and role in star formation. The largest filaments can reach up to Galactic scale as part of the spiral arm structure. However, such large scale filaments are hard to identify systematically due to limitations in identifying methodology (i.e., as extinction features). We present a new approach to directly search for the largest, coldest, and densest filaments in the Galaxy, making use of sensitive Herschel Hi-GAL data complemented by spectral line cubes. We present a sample of the 9 most prominent Herschel filaments, including 6 identified from a pilot search field plus 3 from outside the field. These filaments measure 37-99 pc long and 0.6-3.0 pc wide with masses (0.5-8.3)$\times 10^4{M}_{\odot }$, and beam-averaged ($28"$, or 0.4-0.7 pc) peak H${}_2$ column densities of (1.7-9.3)$\times 10^{22}\mathrm{c}{\mathrm{m}}^{-2}$. The bulk of the filaments are relatively cold (17-21 K), while some local clumps have a dust temperature up to 25-47 K. All the filaments are located within <~60 pc from the Galactic mid-plane. Comparing the filaments to a recent spiral arm model incorporating the latest parallax measurements, we find that 7/9 of them reside within arms, but most are close to arm edges. These filaments are comparable in length to the Galactic scale height and therefore are not simply part of a grander turbulent cascade.

Published 2015MNRAS.450.4043W; this version contains minor proof corrections. FT-based background removal code at https://github.com/esoPanda/FTbg SED fitting code at http://hi-gal-sed-fitter.readthedocs.org 3D interactive visualization at http://www.eso.org/~kwang

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• A Census of Large-Scale ($\ge$ 10 pc), Velocity-Coherent, Dense Filaments in the Northern Galactic Plane: Automated Identification Using Minimum Spanning Tree
• Thermal Feedback in the high-mass star and cluster forming region W51
• Interstellar filaments and star formation
• The evolution of Giant Molecular Filaments
• Temperature structure and kinematics of the IRDC G035.39-00.33
• A multi-wavelength observation and investigation of six infrared dark clouds
• Gas kinematics and star formation in the filamentary molecular cloud G47.06+0.26
• Search for grain growth towards the center of L1544
• Revealing a spiral-shaped molecular cloud in our galaxy - Cloud fragmentation under rotation and gravity
• Probing the massive star forming environment - a multiwavelength investigation of the filamentary IRDC G333.73+0.37
• Formation of Galactic Prominence in Galactic Central Region