Abstract
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 överheating" 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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