Prog. Theor. Phys. Vol. 78 No. 6 (1987) pp. 1273-1287

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Fragmentation of Isothermal Sheet-Like Clouds. II

— Full Nonlinear Numerical Simulations —

Shoken M. Miyama, Shinji Narita^* and Chushiro Hayashi^**

Department of Physics, Kyoto University, Kyoto 606
^*Department of Electronics, Dōshisha University, Kyoto 602
^**Momoyama Yogoro-cho 1, Fushimi-ku, Kyoto 612

(Received August 24, 1987)

Abstract:

The fragmentational instability of an infinite isothermal gas layer, extending infinitely in the x- and y-direction, is investigated by means of three-dimensional numerical simulations. The nonlinear growth of perturbations with the initial wave pattern, cos(k_xx) ×cos(k_yy), is calculated for various values of the wave numbers k_x and k_y. For unstable modes, the fragmentation of a layer and the subsequent collapse of fragments are simulated. It is found that, if the ratio, k_y/k_x, is in the range, 0.8-1.2, each fragment collapses almost axisymmetrically without flattering along the z-axis. However, if the ratio is greater than 1.2 or less than 0.8, each fragment becomes more and more slender as it collapse and finally a thin filament is formed. We also calculate the growth of random perturbations and confirm that a large number of filaments are formed.
As a result of the computations, we construct a scenario of fragmentation and subsequent evolution of a sheet-like cloud such that most of the fragments become finally thin filaments and re-fragment. This scenario explains why filamentary structures often appear in interstellar clouds observed. We also find that the mass function of the final fragments is expressed in the form N ∝m^-2, where N and m are the number and mass, respectively.

URL : http://ptp.ipap.jp/link?PTP/78/1273/
DOI : 10.1143/PTP.78.1273

References:

S. M. Miyama, S. Narita and C. Hayashi, Prog. Theor. Phys. 78 (1987), 1051[IPAP]. (Paper I)
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