Large-scale filaments associated with Milky Way spiral arms
Date Issued
2015
Author(s)
Wang, Ke
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•
Ginsburg, Adam
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Walmsley, C. Malcolm
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•
Description
We are grateful to Mark Reid for discussion on Galactic spiral arms and kinematic distance, and to Phil Myers, Andreas Burkert, Thomas Henning, Henrik Beuther, Sarah Ragan, and John Bally for inspiring discussion. We appreciate an anonymous referee's valuable comments that helped clarify the manuscript. KW and AG acknowledge support from the ESO fellowship. This study is part of the research project WA3628-1/1 led by KW through the DFG priority programme 1573 (‘Physics of the Interstellar Medium’). Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. This publication is based on data acquired with the APEX through ESO programme 092.C-0713. APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory. This publication makes use of molecular line data from the Boston University-FCRAO GRS. The GRS is a joint project of Boston University and Five College Radio Astronomy Observatory, funded by the National Science Foundation under grants AST-9800334, AST-0098562, and AST-0100793. This research made use of open-source python packages astropy (astropy.org), glue (glueviz.org) and pvextractor ( pvextractor.readthedocs.org ).
Abstract
The ubiquity of filamentary structure at various scales throughout 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 (Herschel Infrared Galactic Plane Survey) data complemented by spectral line cubes. We present a sample of the nine most prominent Herschel filaments, including six identified from a pilot search field plus three from outside the field. These filaments measure 37-99 pc long and 0.6-3.0 pc wide with masses (0.5-8.3) × 104 M☉, and beam-averaged (28 arcsec, or 0.4-0.7 pc) peak H2 column densities of (1.7-9.3)× 1022 cm- 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 scaleheight and therefore are not simply part of a grander turbulent cascade.
Volume
450
Issue
4
Start page
4043
Issn Identifier
0035-8711
Ads BibCode
2015MNRAS.450.4043W
Rights
open.access
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