Journal
ASTROPHYSICAL JOURNAL
Volume 761, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/761/2/149
Keywords
hydrodynamics; ISM: kinematics and dynamics; ISM: structure; methods: numerical; shock waves; turbulence
Categories
Funding
- International Max Planck Research School for Astronomy and Cosmic Physics (IMPRS-A)
- Heidelberg Graduate School of Fundamental Physics (HGSFP)
- Excellence Initiative of the German Research Foundation DFG GSC [129/1]
- Baden-Wurttemberg-Stiftung via the program Internationale Spitzenforschung II [P-LS-SPII/18]
- Max-Planck-Institut fur Astrophysik in Garching
- Australian Research Council [DP110102191]
- Deutsche Forschungsgemeinschaft (DFG) [KL 1358/11, SFB 881]
- Heidelberg University
- German Excellence Initiative
- Leibniz Rechenzentrum [h0972, pr32lo]
- Forschungszentrum Julich [hhd20]
- DOE
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The probability density function of the gas density in subsonic and supersonic, isothermal, driven turbulence is analyzed using a systematic set of hydrodynamical grid simulations with resolutions of up to 1024(3) cells. We perform a series of numerical experiments with root-mean-square (rms) Mach number M ranging from the nearly incompressible, subsonic (M = 0.1) to the highly compressible, supersonic (M = 15) regime. We study the influence of two extreme cases for the driving mechanism by applying a purely solenoidal (divergence-free) and a purely compressive (curl-free) forcing field to drive the turbulence. We find that our measurements fit the linear relation between the rms Mach number and the standard deviation (std. dev.) of the density distribution in a wide range of Mach numbers, where the proportionality constant depends on the type of forcing. In addition, we propose a new linear relation between the std. dev. of the density distribution sigma(rho) and that of the velocity in compressible modes, i.e., the compressible component of the rms Mach number, M-comp. In this relation the influence of the forcing is significantly reduced, suggesting a linear relation between sigma(rho) and M-comp, independent of the forcing, and ranging from the subsonic to the supersonic regime.
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