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Published 1979 | Published
Book Section - Chapter Open

Giant molecular clouds in the galaxy: distribution, mass, size and age


Millimeter wave observations of emission from the CO molecule have become, over the past eight years, the dominant method for determining the physical properties of dense interstellar clouds, composed primarily of molecular hydrogen and for exploring the structure and kinematics of the galactic disk. In this paper we briefly review the CO survey results in the literature (Section 2) and then present new results (Section 3-7) of an extensive ^(13)CO and ^(12)CO survey of the galactic distribution, size, mass and age of molecular clouds. The interpretation of this survey leads to a new picture of the interstellar medium dominated by very massive stable long-lived clouds which we refer to as Giant Molecular Clouds. We find that Giant Molecular Clouds (GMC's) with M = 10^5–3 × 10^6 M⊙ are a major constituent of the galactic disk, the dominant component of the interstellar medium in the galaxy interior to the sun and the most massive objects in the galaxy. We find that the interstellar medium and star formation are dominated by massive gravitationally bound clouds in which stars and associations are forming but at a very low rate in comparison to the free fall time. The galactic distribution of the molecules as traced by CO emission is interpreted as the distribution of GMC's. As the most massive objects in the galaxy they are also basic to the dynamics of the disk.

Additional Information

© 1979 by the IAU. This work has been supported in part by NSF Grant AST 77-23419 at the State University of New York at Stony Brook.

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Published - giant_molecular_clouds_in_the_galaxy_distribution_mass_size_and_age.pdf



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August 19, 2023
January 14, 2024