Radiation-Hydrodynamic Simulations of the Formation of Orion-Like Star Clusters II. The Initial Mass Function from Winds, Turbulence, and Radiation

Details Radiation-Hydrodynamic Simulations of the Formation of Orion-Like Star Clusters II. The Initial Mass Function from Winds, Turbulence, and Radiation Radiation-Hydrodynamic Simulations of the Formation of Orion-Like Star Clusters II. The Initial Mass Function from Winds, Turbulence, and Radiation

2012-03-12

arxiv.org/abs/1203.2620v1

Astronomy and Astrophysics

Astrophysics

Solar and Stellar Astrophysics

17 pages, 15 figures, emulateapj format, submitted to ApJ. For movies of the results, see http://www.ucolick.org/~krumholz/dow

Scientific paper

[abridged] We report simulations of the formation of a star cluster similar to the Orion Nebula Cluster (ONC), including both radiative transfer and protostellar outflows, and starting from both smooth and self-consistently turbulent initial conditions. Our calculations form hundreds of stars and brown dwarfs, yielding a stellar mass distribution that is well-sampled from <0.1 Msun to >10 Msun. We show that a simulation that begins with turbulent density and velocity fields embedded in a larger turbulent volume, and that includes protostellar outflows, produces an excellent fit to the observed initial mass function (IMF) of the ONC. This is the first simulation published to date that reproduces the observed IMF in a cluster large enough to contain massive stars, and where the peak of the mass function is determined by a fully self-consistent calculation of gas thermodynamics rather than a hand-imposed equation of state. This simulation also produces a star formation rate that, while still too high, is much closer to observed values than in any other case. Moreover, we show that the combination of outflows and turbulence yields an IMF that is invariant with time, resolving the "overheating" problem in which simulations without these features have an IMF peak that shifts to progressively higher masses over time as more and more of the gas is heated, inconsistent with the observed invariance of the IMF. The simulation that matches the observed IMF also reproduces the observed trend of stellar multiplicity strongly increasing with mass. This simulation produces massive stars from distinct massive cores whose properties are consistent with those of observed massive cores. However, the stars formed in these cores also undergo dynamical interactions as they accrete that naturally produce Trapezium-like hierarchical multiple systems of massive stars.

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