Other
Scientific paper
Dec 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aas...197.4216v&link_type=abstract
American Astronomical Society, 197th AAS Meeting, #42.16; Bulletin of the American Astronomical Society, Vol. 32, p.1468
Other
Scientific paper
We explore the dissipative ability of numerical simulations of compressible MHD turbulence that represent the interstellar medium at intermediate-to-large scales. Turbulent kinetic energy Ek is injected realistically into the medium by means of randomly placed ``stars'', which radially accelerate their surrounding medium. We characterize the input sources by their size lf and by the rate ˙ {E}i,s at which each one injects energy into the flow. A third important parameter is ˙ ΣOB, the rate of formation of ``OB stars''. The spatially-scattered, small-scale nature of the injection (``forcing'') gives rise to the coexistence of both forced and decaying turbulent regimes within the same flow. In the forced regime, the global dissipation rate is always very similar to the injection rate, implying that most of the energy is dissipated in the vicinity of the sources. The characteristic dissipation time is given approximately by ti>= < (Σg> urms2Ei,s˙)/(ΣOB), where <Σg> is the average gas surface density, urms is the rms velocity dispersion, and Ei,s is the net kinetic energy input per source. Since urms also depends on the other injection parameters, it turns out that the dissipation time is nearly independent of ˙ {E}i,s and of ˙ ΣOB, the dominant parameter being lf. Empirically, we find that ti lf0.7. For realistic values of the parameters, ti≈ 15-25 Myr. In the decaying regime, the kinetic energy decays with time as ~ t-0.8. This time dependence can be translated into a distance dependence. We discuss the implications of our results for models of galaxy formation and evolution. This research has received partial funding from Conacyt grant 27752-E.
Avila-Reese Vladimir
Vázquez-Semadeni Enrique
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