Year: 2012
Type: article
Abstract: We show that supersonic MHD turbulence yields a star formation rate (SFR) as low as observed in molecular clouds, for characteristic values of the free-fall time divided by the dynamical time, t ff / t dyn , the Alfvénic Mach number, , and the sonic Mach number, . Using a very large set of deep adaptive-mesh-refinement simulations, we quantify the dependence of the SFR per free-fall time, ff , on the above parameters. Our main results are (1) that ff decreases exponentially with increasing t ff / t dyn , but is insensitive to changes in , for constant values of t ff / t dyn and . (2) Decreasing values of (stronger magnetic fields) reduce ff , but only to a point, beyond which ff increases with a further decrease of . (3) For values of characteristic of star-forming regions, ff varies with by less than a factor of two. We propose a simple star formation law, based on the empirical fit to the minimum ff , and depending only on t ff / t dyn : ff ≈ wind exp (− 1.6 t ff / t dyn ). Because it only depends on the mean gas density and rms velocity, this law is straightforward to implement in simulations and analytical models of galaxy formation and evolution.
Authors: Paolo Padoan, Troels Haugbølle, Åke Nordlund
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W1975358135