Are turbulent spheres suitable initial conditions for star-forming clouds?
Monthly Notices of the Royal Astronomical Society: Letters
Oxford University Press for Royal Astronomical Society
To date, most numerical simulations of molecular clouds, and star formation within them, assume a uniform density sphere or box with an imposed turbulent velocity field. In this work, we select molecular clouds from galactic scale simulations as initial conditions, increase their resolution, and re-simulate them using the smoothed particle hydrodynamics code gadget2. Our approach provides clouds with morphologies, internal structures and kinematics that constitute more consistent and realistic initial conditions for simulations of star formation. We perform comparisons between molecular clouds derived from a galactic simulation, and spheres of turbulent gas of similar dimensions, mass and velocity dispersion. We focus on properties of the clouds such as their density, velocity structure and star formation rate. We find that the inherited velocity structure of the galactic clouds has a significant impact on the star formation rate and evolution of the cloud. Our results indicate that, although we can follow the time evolution of star formation in any simulated cloud, capturing the entire history is difficult as we ignore any star formation that might have occurred before initialization. Overall, the turbulent spheres do not match the complexity of the galactic clouds.
We thank an anonymous referee for suggestions which helped improve the Letter, and Paul Clark for comments on an earlier draft. The calculations for this Letter were performed on the University of Exeter Supercomputer, a DiRAC Facility jointly funded by STFC, the Large Facilities Capital Fund of BIS, and the University of Exeter. RRR, CLD and ADC acknowledge funding from the European Research Council for the FP7 ERC starting grant project LOCALSTAR. Figs 1, 2 and 5 were produced using SPLASH (Price 2007)
Copyright © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
This is the final version of the article. Available from OUP via the DOI in this record.
Vol. 446 (1), pp. L46-L50