  We report the results of a series of AMR radiation-hydrodynamic simulations
of the collapse of massive star forming clouds using the ORION code. These
simulations are the first to include the feedback effects protostellar
outflows, as well as protostellar radiative heating and radiation pressure
exerted on the infalling, dusty gas. We find that that outflows evacuate polar
cavities of reduced optical depth through the ambient core. These enhance the
radiative flux in the poleward direction so that it is 1.7 to 15 times larger
than that in the midplane. As a result the radiative heating and outward
radiation force exerted on the protostellar disk and infalling cloud gas in the
equatorial direction are greatly diminished. The simultaneously reduces the
Eddington radiation pressure barrier to high-mass star formation and increases
the minimum threshold surface density for radiative heating to suppress
fragmentation compared to models that do not include outflows. The strength of
both these effects depends on the initial core surface density. Lower surface
density cores have longer free-fall times and thus massive stars formed within
them undergo more Kelvin contraction as the core collapses, leading to more
powerful outflows. Furthermore, in lower surface density clouds the ratio of
the time required for the outflow to break out of the core to the core
free-fall time is smaller, so that these clouds are consequently influenced by
outflows at earlier stages of collapse. As a result, outflow effects are
strongest in low surface density cores and weakest in high surface density one.
We also find that radiation focusing in the direction of outflow cavities is
sufficient to prevent the formation of radiation pressure-supported
circumstellar gas bubbles, in contrast to models which neglect protostellar
outflow feedback.
