The equilibrium state of molecular regions in the outer galaxy

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Astrophysical Journal, ISSN: 1538-4357, Vol: 551, Issue: 2 PART 1, Page: 852-866

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Mark H. Heyer; Ronald L. Snell; John M. Carpenter
IOP Publishing
Physics and Astronomy; Earth and Planetary Sciences; Galaxy : kinematics and dynamics; Galaxy : structure; ISM : clouds; ISM : general; ISM : kinematics and dynamics; ISM : molecules; Astrophysics and Astronomy; Astrophysics
article description
A summary of global properties and an evaluation of the equilibrium state of molecular regions in the outer Galaxy are presented from the decomposition of the FCRAO Outer Galaxy Survey and targetedCO andCO observations of four giant molecular cloud complexes. The ensemble of identified objects includes both small, isolated clouds and clumps within larger cloud complexes. TheCO luminosity function and size distribution of a subsample of objects with well-defined distances are determined such that ΔJV/ΔL= (3 × 10)Land ΔJV/Δr= (1.7 × 10)r.CO velocity dispersions show little variation with cloud sizes for radii less than 10 pc. It is demonstrated that the internal motions of regions with M= XL> 10Mare bound by self-gravity, yet the constituent clumps of cloud complexes and isolated molecular clouds with M< 10Mare not in self-gravitational equilibrium. The required external pressures to maintain the equilibrium of this population are (1-2) × 10cmK.