Large-scale filaments associated with Milky Way spiral arms
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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 2015
- DOI:
- 10.1093/mnras/stv735
- arXiv:
- arXiv:1504.00647
- Bibcode:
- 2015MNRAS.450.4043W
- Keywords:
-
- catalogues;
- stars: formation;
- ISM: clouds;
- ISM: structure;
- Galaxy: structure;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Published 2015MNRAS.450.4043W