Abstract
ABSTRACT The all-Galaxy CO survey of Dame et al. is by far the most uniform, large-scale Galactic CO survey. Using a dendrogram-based decomposition of this survey, we present a catalog of 1064 massive molecular clouds throughout the Galactic plane. This catalog contains 2.5 × 108 solar masses, or 25 − 5.8 + 10.7 % of the Milky Way's estimated H2 mass. We track clouds in some spiral arms through multiple quadrants. The power index of Larson's first law, the size-linewidth relation, is consistent with 0.5 in all regions—possibly due to an observational bias—but clouds in the inner Galaxy systematically have significantly (∼30%) higher linewidths at a given size, indicating that their linewidths are set in part by the Galactic environment. The mass functions of clouds in the inner Galaxy versus the outer Galaxy are both qualitatively and quantitatively distinct. The inner Galaxy mass spectrum is best described by a truncated power law with a power index of γ = −1.6 ± 0.1 and an upper truncation mass of M 0 = (1.0 ± 0.2) × 107 M ⊙, while the outer Galaxy mass spectrum is better described by a non-truncating power law with γ = −2.2 ± 0.1 and an upper mass of M 0 = (1.5 ± 0.5) × 106 M ⊙, indicating that the inner Galaxy is able to form and host substantially more massive GMCs than the outer Galaxy. Additionally, we have simulated how the Milky Way would appear in CO from extragalactic perspectives, for comparison with CO maps of other galaxies.
Highlights
Giant molecular clouds (GMCs) are the fundamental building blocks of star formation in disk galaxies; studying their properties and structure clarifies our understanding of the initial conditions of star formation
We have learned that molecular star-forming gas is concentrated in large, discrete clouds with a low volume-filling factor, with masses 104 − 106 M and above; gas is concentrated along spiral arms; clouds have virialized internal motions, producing an observed relation between cloud size and spectral line-width (Larson 1981); and that the mass distribution function of GMCs has a negative slope, with power law index ∼ −1.5 previously measured in the Galaxy
We have developed a technique that relies on dendrograms to identify what regions of emission correspond to GMCs, while avoiding the need to assume a background emission model
Summary
The Harvard community has made this article openly available. Please share how this access benefits you. The Astrophysical Journal 822 (1) (May 4): 52. A Uniform Catalog of Molecular Clouds in the Milky Way arXiv:1602.02791v1 [astro-ph.GA] 8 Feb 2016. Bergin , Christopher Beaumont , and T. M. Dame , : Department of Astronomy, University of Michigan, 311 West Hall, 1085 South University. 2: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
