A turbulent-entropic instability and the fragmentation of star-forming clouds. Issue 4 (28th January 2020)

• Record Type: Journal Article
• Authors: Keto, Eric; Field, George B; Blackman, Eric G
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 492:Issue 4(2020)
• Page Start: 5870
• Page End: 5877
• Publication Date: 2020-01-28
• Subjects: instabilities -- stars: formation -- ISM: evolution; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa230
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: The kinetic energy of supersonic turbulence within interstellar clouds is subject to cooling by dissipation in shocks and subsequent line radiation. The clouds are therefore susceptible to a condensation process controlled by the specific entropy. In a form analogous to the thermodynamic entropy, the entropy for supersonic turbulence is proportional to the log of the product of the mean turbulent velocity and the size scale. We derive a dispersion relation for the growth of entropic instabilities in a spherical self-gravitating cloud and find that there is a critical maximum dissipation time-scale, about equal to the crossing time, that allows for fragmentation and subsequent star formation. However, the time-scale for the loss of turbulent energy may be shorter or longer, for example, with rapid thermal cooling or the injection of mechanical energy. Differences in the time-scale for energy loss in different star-forming regions may result in differences in the outcome, for example, in the initial mass function.