Turbulent Gas Flows in the Rosette and G216‐2.5 Molecular Clouds: Assessing Turbulent Fragmentation Descriptions of Star Formation

Abstract

The role of turbulent fragmentation in regulating the efficiency of star formation in interstellar clouds is examined from new wide-field imaging of 12CO and 13CO J = 1-0 emission from the Rosette and G216-2.5 molecular clouds. The Rosette molecular cloud is a typical star-forming giant molecular cloud, and G215-2.5 is a massive molecular cloud with no OB stars and very little low-mass star formation. The properties of the turbulent gas flow are derived from the set of eigenvectors and eigenimages generated by principal component analysis (PCA) of the spectroscopic data cubes. While the two clouds represent quite divergent states of star formation activity, the velocity structure functions for both clouds are similar. The sonic scale, λS, defined as the spatial scale at which turbulent velocity fluctuations are equivalent to the local sound speed, and the turbulent Mach number evaluated at 1 pc, M1 pc, are derived for an ensemble of clouds including the Rosette and G216-2.5 regions that span a large range in star formation activity. We find no evidence for the positive correlations between these quantities and the star formation efficiency that are predicted by turbulent fragmentation models. A correlation does exist between the star formation efficiency and the sonic scale for a subset of clouds with LFIR/M(H2) > 1 that are generating young stellar clusters. Turbulent fragmentation must play a limited and nonexclusive role in determining the yield of stellar masses within interstellar clouds.