The Equilibrium State of Molecular Regions in the Outer Galaxy

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The Astrophysical Journal, ISSN: 0004-637X, Vol: 551, Issue: 2, Page: 852-866

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Mark H. Heyer; John M. Carpenter; Ronald L. Snell
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
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 targeted CO and CO observations of four giant molecular cloud complexes. The ensemble of identified objects includes both small, isolated clouds and clumps within larger cloud complexes. The CO luminosity function and size distribution of a subsample of objects with well-defined distances are determined such that ΔJV/ΔL = (3 × 10)L and 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 > 10 M are bound by self-gravity, yet the constituent clumps of cloud complexes and isolated molecular clouds with M < 10M are not in self-gravitational equilibrium. The required external pressures to maintain the equilibrium of this population are (1-2) × 10 cm K.