Journal Article

The dependence of star formation on initial conditions and molecular cloud structure

Matthew R. Bate

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 397, issue 1, pages 232-248
Published in print July 2009 | ISSN: 0035-8711
Published online July 2009 | e-ISSN: 1365-2966 | DOI:
The dependence of star formation on initial conditions and molecular cloud structure

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We investigate the dependence of stellar properties on the initial kinematic structure of the gas in star-forming molecular clouds. We compare the results from two large-scale hydrodynamical simulations of star cluster formation that resolve the fragmentation process down to the opacity limit, the first of which was reported by Bate, Bonnell & Bromm. The initial conditions of the two calculations are identical, but in the new simulation the power spectrum of the velocity field imposed on the cloud initially and allowed to decay is biased in favour of large-scale motions. Whereas the calculation of Bate et al. began with a power spectrum P(k) ∝k−4 to match the Larson scaling relations for the turbulent motions observed in molecular clouds, the new calculation begins with a power spectrum P(k) ∝k−6.

Despite this change to the initial motions in the cloud and the resulting density structure of the molecular cloud, the stellar properties resulting from the two calculations are indistinguishable. This demonstrates that the results of such hydrodynamical calculations of star cluster formation are relatively insensitive to the initial conditions. It is also consistent with the fact that the statistical properties of stars and brown dwarfs (e.g. the stellar initial mass function) are observed to be relatively invariant within our Galaxy and do not appear to depend on environment.

Keywords: hydrodynamics; binaries: general; stars: formation; stars: low-mass, brown dwarfs; stars: luminosity function, mass function; ISM: clouds

Journal Article.  13244 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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