Molecular cloud formation by gravitational instabilities in a clumpy interstellar medium

Journal Article · Fri Sep 01 04:00:00 EDT 1989 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/167798· OSTI ID:5288341

Elmegreen, B G ^[1]

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1. IBM Thomas J. Watson Research Center, Yorktown Heights, NY (USA)

A dispersion relation is derived for gravitational instabilities in a medium with cloud collisional cooling, using a time-dependent energy equation instead of the adiabatic equation of state. The instability extends to much smaller length scales than in the conventional Jeans analysis, and, in regions temporarily without cloud stirring, it has a large growth rate down to the cloud collision mean free path. These results suggests that gravitational instabilities in a variety of environments, such as galactic density wave shocks, swept-up shells, and extended, quiescent regions of the interstellar medium, can form molecular clouds with masses much less than the conventional Jeans mass, e.g., from 100 to 10 million solar masses for the ambient medium, and they can do this even when the unperturbed velocity dispersion remains high. Similar processes operating inside existing clouds might promote gravitationally driven fragmentation. 29 refs.

• OSTI ID: 5288341
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 344; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ASTROPHYSICS
COSMIC GASES
FLUIDS
GASES
GRAVITATION
GRAVITATIONAL COLLAPSE
GRAVITATIONAL INSTABILITY
INSTABILITY
INTERSTELLAR SPACE
MASS
MASS SPECTRA
PLASMA INSTABILITY
SPACE
SPECTRA
TIME DEPENDENCE