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

Published online by Cambridge University Press:  14 August 2015

P. M. Solomon ,
D. B. Sanders  and
N. Z. Scoville
P. M. Solomon
Affiliation:
Astronomy Program, State University of New York, Stony Brook, N.Y.
D. B. Sanders
Affiliation:
Astronomy Program, State University of New York, Stony Brook, N.Y.
N. Z. Scoville
Affiliation:
Astronomy Dept., University of Massachusetts, Amherst, Mass.

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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 13CO and 12CO 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 = 105–3 × 106M⊙ 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.

Type
II. THE DISK COMPONENT
Information
Symposium - International Astronomical Union , Volume 84: The Large-Scale Characteristics of the Galaxy , 1979 , pp. 35 - 52
Copyright
Copyright © Reidel 1979 

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