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

TL;DR

This study compares two hydrodynamical simulations of star cluster formation with different initial velocity spectra, finding that stellar properties are largely unaffected by initial conditions, indicating a robustness in star formation outcomes.

Contribution

It demonstrates that the statistical properties of stars and brown dwarfs are insensitive to initial gas velocity structures in molecular clouds.

Findings

Stellar properties are similar despite different initial velocity spectra.

Star formation outcomes are robust against variations in initial conditions.

Supports the observed invariance of the initial mass function across environments.

Abstract

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 and 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 resulting 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.