The Star Formation Rate of Molecular Clouds
This is the author accepted manuscript available from arXiv.org via the DOI in this record.
We review recent advances in the analytical and numerical modeling of the star formation rate in molecular clouds and discuss the available observational constraints. We focus on molecular clouds as the fundamental star formation sites, rather than on the larger-scale processes that form the clouds and set their properties. Molecular clouds are shaped into a complex filamentary structure by supersonic turbulence, with only a small fraction of the cloud mass channeled into collapsing protostars over a free-fall time of the system. In recent years, the physics of supersonic turbulence has been widely explored with computer simulations, leading to statistical models of this fragmentation process, and to the prediction of the star formation rate as a function of fundamental physical parameters of molecular clouds, such as the virial parameter, the rms Mach number, the compressive fraction of the turbulence driver, and the ratio of gas to magnetic pressure. Infrared space telescopes, as well as ground-based observatories have provided unprecedented probes of the filamentary structure of molecular clouds and the location of forming stars within them.
PP is supported by the FP7-PEOPLE- 2010-RG grant PIRG07-GA-2010- 261359. Simulations by PP were carried out on the NASA/Ames Pleiades supercomputer, and under the PRACE project pra50751 running on SuperMUC at the LRZ (project ID pr86li). CF thanks for support from the Australian Research Council for a Discovery Projects Fellowship (Grant DP110102191). NJE was supported by NSF Grant AST-1109116 to the University of Texas at Austin. The research of CFM is supported in part by NSF grant AST-1211729 and NASA grant NNX13AB84G. DJ is supported by the National Research Council of Canada and by a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant. JKJ is supported by a Lundbeck Foundation Junior Group Leader Fellowship. Research at Centre for Star and Planet Formation was funded by the Danish National Research Foundation and the University of Copenhagens Programme of Excellence. Supercomputing time at Leibniz Rechenzentrum (PRACE projects pr86li, pr89mu, and project pr32lo), at Forschungszentrum J¨ulich (project hhd20), and at DeIC/KU in Copenhagen are gratefully acknowledged.
24 pages, 5 figures, Accepted for publication as a chapter in Protostars and Planets VI, University of Arizona Press (2014), eds. H. Beuther, R. S. Klessen, C. P. Dullemond, Th. Henning