A simple law of star formation
Publikation: Bidrag til tidsskrift › Letter › Forskning › fagfællebedømt
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A simple law of star formation. / Padoan, Paolo; Haugbølle, Troels; Nordlund, Åke.
I: The Astrophysical Journal Letters, Bind 759, L27, 2012.Publikation: Bidrag til tidsskrift › Letter › Forskning › fagfællebedømt
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TY - JOUR
T1 - A simple law of star formation
AU - Padoan, Paolo
AU - Haugbølle, Troels
AU - Nordlund, Åke
PY - 2012
Y1 - 2012
N2 - 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, {\cal M}_a, and the sonic Mach number, {\cal M}_s. Using a very large set of deep adaptive-mesh-refinement simulations, we quantify the dependence of the SFR per free-fall time, epsilonff, on the above parameters. Our main results are (1) that epsilonff decreases exponentially with increasing t ff/t dyn, but is insensitive to changes in {\cal M}_s, for constant values of t ff/t dyn and {\cal M}_a. (2) Decreasing values of {\cal M}_a (stronger magnetic fields) reduce epsilonff, but only to a point, beyond which epsilonff increases with a further decrease of {\cal M}_a. (3) For values of {\cal M}_a characteristic of star-forming regions, epsilonff varies with {\cal M}_a by less than a factor of two. We propose a simple star formation law, based on the empirical fit to the minimum epsilonff, and depending only on t ff/t dyn: epsilonff ˜ epsilonwindexp (– 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.
AB - 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, {\cal M}_a, and the sonic Mach number, {\cal M}_s. Using a very large set of deep adaptive-mesh-refinement simulations, we quantify the dependence of the SFR per free-fall time, epsilonff, on the above parameters. Our main results are (1) that epsilonff decreases exponentially with increasing t ff/t dyn, but is insensitive to changes in {\cal M}_s, for constant values of t ff/t dyn and {\cal M}_a. (2) Decreasing values of {\cal M}_a (stronger magnetic fields) reduce epsilonff, but only to a point, beyond which epsilonff increases with a further decrease of {\cal M}_a. (3) For values of {\cal M}_a characteristic of star-forming regions, epsilonff varies with {\cal M}_a by less than a factor of two. We propose a simple star formation law, based on the empirical fit to the minimum epsilonff, and depending only on t ff/t dyn: epsilonff ˜ epsilonwindexp (– 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.
U2 - 10.1088/2041-8205/759/2/L27
DO - 10.1088/2041-8205/759/2/L27
M3 - Letter
VL - 759
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
M1 - L27
ER -
ID: 42036930