Dense cores in dark clouds. III. Subsonic turbulence

Journal Article · Fri Jul 01 04:00:00 EDT 1983 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/161101· OSTI ID:5668239

Myers, P C

In 43 dark clouds with narrow molecular lines, significant correlations exist between line width and map size of the form ..delta..vproportionalR/sup 0.5/, and between mean density and map size of the form nproportionalR/sup -1/; and the law of virial equilibrium is closely satisfied. These relations tend to confirm those found earlier for larger clouds, and extend them into the regime of subsonic turbulence. If these relations for large and small clouds reflect the same process, it is still unclear whether this process is a turbulent energy cascade, as in Kolmogorov turbulence, or simply the tendency of clouds with nproportionalR/sup -1/ to be in virial equilibrium. For the smallest clouds (''dense cores'') there is weak support for the turbulent cascade picture. In this picture viscous dissipation of turbulence is likely to play an important role in heating and star formation. The time scale for the free decay of turbulence in dense cores is < or approx. =5 x 10/sup 5/ yr, comparable to the free-fall time. Dense cores can thus form low-mass stars on free-fall time scales if their input of fresh turbulence is sufficiently reduced. This reduction may occur as a result of their small size, or their high density contrast with surrounding gas. Observed distributions of dense core properties in Taurus, Ophiuchus, and other dark cloud regions appear consistent with dense core evolution toward star formation via dissipation of turbulence. In complexes which are vigorously forming low-mass stars, dense cores are more prevalent, smaller, denser, and have narrower lines than in regions with less star formation.

• Research Organization: Harvard-Smithsonian Center for Astrophysics
• OSTI ID: 5668239
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 270:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics &amp; Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DISSIPATION FACTOR
GRAVITATION
HEATING
INTERSTELLAR GRAINS
LINE WIDTHS
MOLECULES
NEBULAE
PARTICLES
STAR ACCRETION
STAR EVOLUTION
TURBULENCE
VISCOSITY