Cluster Formation in Contracting Molecular Clouds

Abstract

We explore, through a simplified, semi-analytic model, the formation of dense clusters containing massive stars. The parent cloud spawning the cluster is represented as an isothermal sphere. This sphere is in near force balance between self-gravity and turbulent pressure. Self-gravity, mediated by turbulent dissipation, drives slow contraction of the cloud, eventually leading to a sharp central spike in density and the onset of dynamical instability. We suggest that, in a real cloud, this transition marks the late and rapid production of massive stars. We also offer an empirical prescription, akin to the Schmidt law, for low-mass star formation in our contracting cloud. Applying this prescription to the Orion Nebula Cluster, we are able to reproduce the accelerating star formation previously inferred from the distribution of member stars in the HR diagram. The cloud turns about 10 percent of its mass into low-mass stars before becoming dynamically unstable. Over a cloud free-fall time, this figure drops to 1 percent, consistent with the overall star formation efficiency of molecular clouds in the Galaxy.

To appear in ApJ Vol. 667, September 20

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Cited by in corpus (16)

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• The Herschel view of the dense core population in the Ophiuchus molecular cloud
• Spitzer View of Young Massive Stars in the LMC HII Complexes. II. N159
• Stellar Kinematics of Young Clusters in Turbulent Hydrodynamic Simulations
• Rotational studies in the Orion Nebula Cluster: from solar mass stars to brown dwarfs
• The Orbital Decay of Embedded Binary Stars
• Star cluster formation with stellar feedback and large-scale inflow
• Mass and luminosity evolution of young stellar objects
• The Distribution of Stellar Mass in the Pleiades
• From large scale gas compression to cluster formation in the Antennae overlap region
• The Accelerating Pace of Star Formation
• Spectral classification and HR diagram of pre-main sequence stars in NGC6530
• The Dynamical Evolution of the Pleiades
• Star formation history of Canis Major OB1 - II. A bimodal X-ray population revealed by XMM-Newton