Cloud fluid compression and softening in spiral arms and the formation of giant molecular cloud complexes

Journal Article · Wed Apr 01 04:00:00 EST 1981 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/158786· OSTI ID:6457753

Cowie, L L

In this, the second paper of a series on the galactodynamics of the cloudy interstellar medium, we consider the response of such a gas to a forcing potential in the tight-winding density wave theory. The cloud fluid is treated in the hydrodynamic limit with an equation of state which softens at high densities. It is shown that in the inner regions of the galaxy, cooling of the cloud fluid in the arms can result in gravitational instability and the formation of large bound complexes of clouds which we identify with the giant molecular clouds (GMCs). Masses dimensions, distributions, and scale heights of the GMCs are predicted by the theory. It is suggested that the interstellar gas density in the disk is regulated by the gravitational instability mechanism in the arms which siphons material into star formation. Implications for the evolution of individual GMCs and for galactic morphology are discussed.

• Research Organization: Princeton University Observatory
• OSTI ID: 6457753
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 245:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COMPRESSION
COSMIC GASES
FLUID FLOW
FLUID MECHANICS
FLUIDS
GALACTIC EVOLUTION
GALAXIES
GASES
GRAVITATION
HYDRODYNAMICS
INSTABILITY
INTERSTELLAR SPACE
MECHANICS
MOLECULES
SPACE