The star formation efficiency and its relation to variations in the initial mass function
arXiv:0803.4053 · doi:10.1111/j.1365-2966.2008.13005.x
Abstract
We investigate how the dynamical state of a turbulently supported, 1000 solar mass, molecular cloud affects the properties of the cluster it forms, focusing our discussion on the star formation efficiency (SFE) and the initial mass function (IMF). A variety of initial energy states are examined in this paper, ranging from clouds with PE = 0.1 KE to clouds with PE = 10 KE, and for both isothermal and piece-wise polytropic equations of state (similar to that suggested by Larson). It is found that arbitrary star formation efficiencies are possible, with strongly unbound clouds yielding very low star formation efficiencies. We suggest that the low star formation efficiency in the Maddelena cloud may be a consequence of the relatively unbound state of its internal structure. It is also found that competitive accretion results in the observed IMF when the clouds have initial energy states of PE >= KE. We show that under such conditions the shape of the IMF is independent of time in the calculations. This demonstrates that the global accretion process can be terminated at any stage in the cluster's evolution, while still yielding a distribution of stellar masses that is consistent with the observed IMF. As the clouds become progressively more unbound, competitive accretion is less important and the protostellar mass function flattens. These results predict that molecular clouds should be permeated with a distributed population of stars that follow a flatter than Salpeter IMF.
8 pages, 6 figures, accepted by MNRAS for publictaion. Now available through the 'Online Early' scheme
References in corpus (7)
- Slow Star Formation in Dense Gas: Evidence and Implications
- Simulating the formation of molecular clouds. I. Slow formation by gravitational collapse from static initial conditions
- Simulating the formation of molecular clouds. II. Rapid formation from turbulent initial conditions
- Six Myths on the Virial Theorem for Interstellar Clouds
- The Jeans mass and the origin of the knee in the IMF
- Clump Lifetimes and the Initial Mass Function
- Insights from Simulations of Star Formation