Turbulent driving scales in molecular clouds

被引:139
作者
Brunt, C. M. [1 ]
Heyer, M. H. [2 ]
Mac Low, M. -M. [3 ]
机构
[1] Univ Exeter, Sch Phys, Astrophys Grp, Exeter EX4 4QL, Devon, England
[2] Univ Massachusetts, Dept Astron, Amherst, MA 01003 USA
[3] Amer Museum Nat Hist, Dept Astrophys, New York, NY 10024 USA
关键词
magnetohydrodynamics (MHD); turbulence; techniques: spectroscopic; ISM: molecules; kinematics and dynamics; radio lines: ISM; STAR-FORMATION; GRAVITATIONAL COLLAPSE; VELOCITY MODIFICATION; DRIVEN; DISSIPATION; DENSITY; GAS; UNIVERSALITY; CONSTRAINTS; OUTFLOWS;
D O I
10.1051/0004-6361/200911797
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Context. Supersonic turbulence in molecular clouds is a dominant agent that strongly affects the clouds' evolution and star formation activity. Turbulence may be initiated and maintained by a number of processes, acting at a wide range of physical scales. By examining the dynamical state of molecular clouds, it is possible to assess the primary candidates for how the turbulent energy is injected. Aims. The aim of this paper is to constrain the scales at which turbulence is driven in the molecular interstellar medium, by comparing simulated molecular spectral line observations of numerical magnetohydrodynamic models and molecular spectral line observations of real molecular clouds. Methods. We use principal component analysis, applied to both models and observational data, to extract a quantitative measure of the driving scale of turbulence. Results. We find that only models driven at large scales (comparable to, or exceeding, the size of the cloud) are consistent with observations. This result applies also to clouds with little or no internal star formation activity. Conclusions. Astrophysical processes acting on large scales, including supernova-driven turbulence, magneto-rotational instability, or spiral shock forcing, are viable candidates for the generation and maintenance of molecular cloud turbulence. Small-scale driving by sources internal to molecular clouds, such as outflows, can be important on small scales, but cannot replicate the observed large-scale velocity fluctuations in the molecular interstellar medium.
引用
收藏
页码:883 / 890
页数:8
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