Cloud fragmentation and stellar masses

Abstract

Theoretical arguments and numerical simulations both suggest that a star-forming cloud generally collapses to a flattened or filamentary configuration before fragmenting, and that fragmentation occurs as a result of the gravitational instability of the resulting layer or filament. A number of existing and new results for the stability of polytropic sheets, discs, and filaments are collected in this paper, and critical lengths and masses are derived for a variety of values of the polytropic exponent. The predictions of these stability analyses agree satisfactorily with the results of numerical simulations of the fragmentation of discs and filaments. The predicted critical masses in some well-studied regions of star formation also agree with the typical masses of the observed dense cloud clumps, and, in order of magnitude, with the masses of the young stars.