The star formation efficiency and its relation to variations in the initial mass function

Paul C. Clark, Ian A. Bonnell, Ralf S. Klessen

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)

Abstract

We investigate how the dynamical state of a turbulently supported, 1000 M-circle dot, 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|E-grav| = 0.1 E-kin to clouds with|E-grav| = 10 E-kin, and for both isothermal and piece-wise polytropic equations of state (similar to that suggested by Larson). It is found that arbitrary SFEs are possible, with strongly unbound clouds yielding very low SFEs. We suggest that the low SFE 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 |E-grav| >= E-kin. 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.

Original languageEnglish
Pages (from-to)310
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume386
DOIs
Publication statusPublished - 1 May 2008

Keywords

  • stars : formation
  • stars : fundamental parameters
  • stars : luminosity function
  • mass function
  • galaxies : star clusters
  • SMOOTHED PARTICLE HYDRODYNAMICS
  • GIANT MOLECULAR CLOUDS
  • STELLAR CLUSTERS
  • GRAVITATIONAL COLLAPSE
  • GRAVOTURBULENT FRAGMENTATION
  • VELOCITY DISPERSION
  • SOLAR NEIGHBORHOOD
  • RAPID FORMATION
  • SELF-GRAVITY
  • TURBULENCE

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