TY - JOUR

T1 - Modeling Star Formation as a Markov Process in a Supersonic Gravoturbulent Medium

AU - Scannapieco, Evan

AU - Safarzadeh, Mohammadtaher

N1 - Funding Information:
We thank Tom Abel, Marcus Brüggen, Paolo Padoan, and Enrique Vázquez-Semadeni for useful discussions, and the referee, Mark Krumholz, for his detailed comments. This work was supported by NSF grant AST14-07835 and NASA theory grant NNX15AK82G. We thank the Texas Advanced Computing Center (TACC) and the Extreme Science and Engineering Discovery Environment (XSEDE) for providing HPC resources via grant TG-AST130021.
Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved..

PY - 2018/10/1

Y1 - 2018/10/1

N2 - Molecular clouds exhibit log-normal probability density functions (PDF) of mass densities, which are thought to arise as a consequence of isothermal, supersonic turbulence. Star formation is then widely assumed to occur in perturbations in which gravitational collapse is faster than the rate of change due to turbulent motions. Here we use direct numerical simulations to measure this rate as a function of density for a range of turbulent Mach numbers, and show that it is faster at high densities than at low densities. Furthermore, we show that both the density PDF and rate of change arise naturally in a simple model of turbulence as a continuous Markov process. The one-dimensional Langevin equation that describes this evolution depends on only two parameters, yet it captures the full evolution seen in direct three-dimensional simulations. If it is modified to include gravity, the Langevin equation also reproduces the rate of material collapsing to high densities seen in turbulent simulations including self-gravity. When generalized to include both temperature and density, similar analyses are likely applicable throughout astrophysics.

AB - Molecular clouds exhibit log-normal probability density functions (PDF) of mass densities, which are thought to arise as a consequence of isothermal, supersonic turbulence. Star formation is then widely assumed to occur in perturbations in which gravitational collapse is faster than the rate of change due to turbulent motions. Here we use direct numerical simulations to measure this rate as a function of density for a range of turbulent Mach numbers, and show that it is faster at high densities than at low densities. Furthermore, we show that both the density PDF and rate of change arise naturally in a simple model of turbulence as a continuous Markov process. The one-dimensional Langevin equation that describes this evolution depends on only two parameters, yet it captures the full evolution seen in direct three-dimensional simulations. If it is modified to include gravity, the Langevin equation also reproduces the rate of material collapsing to high densities seen in turbulent simulations including self-gravity. When generalized to include both temperature and density, similar analyses are likely applicable throughout astrophysics.

KW - methods: statistical

KW - stars: formation

KW - turbulence

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U2 - 10.3847/2041-8213/aae1f9

DO - 10.3847/2041-8213/aae1f9

M3 - Article

AN - SCOPUS:85054332269

VL - 865

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

SN - 2041-8205

IS - 2

M1 - L14

ER -