1997/11/28 by Mordecai-Mark Mac Low, Mordecai‐Mark Mac Low, Mac Low, Mordecai-Mark
Physics and Astronomy · #Astrophysics (astro-ph) #Astrophysics and Star Formation Studies #Atomic and Molecular Physics #FOS: Physical sciences #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9711349
In press in The Orion Nebula Revisited, eds. M. J. McCaughrean & A. Burkert (San Francisco, ASP). 15 pages, 6 figures, requires paspconf.sty and psfig.sty. Postscript also available at http://www.mpia-hd.mpg.de/theory/preprints.html#maclow
arxiv created 1997/11/28 · openalex publication_date 1997/11/28 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
This review summarizes the argument for molecular clouds being dominated by turbulence, most likely super-Alfvenic turbulence. Five lines of observational evidence are given: molecular linewidths and line shapes, nonequilibrium chemical abundances, fractal cloud shapes, measurements of the dispersion of dust extinction through clouds, and Zeeman measurements of the field strength. Recent models by Padoan & Nordlund are summarized, that show that super-Alfvenic turbulence appears consistent with these observations. I then present recent computations of my own, with numerical resolution as high as 2563 zones, confirming the basic picture proposed by Padoan & Nordlund, but showing that the decay timescales they quote are actually too long. My computations show that decaying turbulence loses its kinetic energy with a ~1/t dependence on time regardless of whether the turbulence is subsonic, supersonic, isothermal, adiabatic, unmagnetized or magnetized. Finally, the implications for star formation and turbulence theory are discussed.