Charles E. Hansen, Richard I. Klein, Christopher F. McKee, Robert T. Fisher
Protostellar feedback, both radiation and bipolar outflows, dramatically
affects the fragmentation and mass accretion from star-forming cores. We use
ORION, an adaptive mesh refinement gravito-radiation-hydrodynamics code, to
simulate the formation of a cluster of low-mass stars, including both radiative
transfer and protostellar outflows. We ran four simulations to isolate the
individual effects of radiation feedback and outflow feedback as well as the
combination of the two. Outflows reduce protostellar masses and accretion rates
each by a factor of three and therefore reduce protostellar luminosities by an
order of magnitude. Thus, while radiation feedback suppresses fragmentation,
outflows render protostellar radiation largely irrelevant for low-mass star
formation above a mass scale of 0.05 M_sun. We find initial fragmentation of
our cloud at half the global Jeans length, ~ 0.1 pc. With insufficient
protostellar radiation to stop it, these 0.1 pc cores fragment repeatedly,
forming typically 10 stars each. The accretion rate in these stars scales with
mass as predicted from core accretion models that include both thermal and
turbulent motions. We find that protostellar outflows do not significantly
affect the overall cloud dynamics, in the absence of magnetic fields, due to
their small opening angles and poor coupling to the dense gas. The outflows
reduce the mass from the cores by 2/3, giving a core to star efficiency ~ 1/3.
The simulation with radiation and outflows reproduces the observed protostellar
luminosity function. All of the simulations can reproduce observed core mass
functions, though they are sensitive to telescope resolution. The simulation
with both radiation and outflows reproduces the galactic IMF and the two-point
correlation function of the cores observed in rho Oph.
View original:
http://arxiv.org/abs/1201.2751
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