Protostellar Outflows and Radiative Feedback from Massive Stars. II.
  Feedback, Star Formation Efficiency, and Outflow Broadening
  We perform two-dimensional axially symmetric radiation-hydrodynamic
simulations to assess the impact of outflows and radiative force feedback from
massive protostars by varying when the protostellar outflow starts, the ratio
of ejection to accretion rates, and the strength of the wide angle disk wind
component. The star formation efficiency, i.e. the ratio of final stellar mass
to initial core mass, is dominated by radiative forces and the ratio of outflow
to accretion rates. Increasing this ratio has three effects: First, the
protostar grows slower with a lower luminosity at any given time, lowering
radiative feedback. Second, bipolar cavities cleared by the outflow are larger,
further diminishing radiative feedback on disk and core scales. Third, the
higher momentum outflow sweeps up more material from the collapsing envelope,
decreasing the protostar's potential mass reservoir via entrainment. The star
formation efficiency varies with the ratio of ejection to accretion rates from
50% in the case of very weak outflows to as low as 20% for very strong
outflows. At latitudes between the low density bipolar cavity and the high
density accretion disk, wide angle disk winds remove some of the gas, which
otherwise would be part of the accretion flow onto the disk; varying the
strength of these wide angle disk winds, however, alters the final star
formation efficiency by only +/-6%. For all cases, the opening angle of the
bipolar outflow cavity remains below 20 degree during early protostellar
accretion phases, increasing rapidly up to 65 degree at the onset of radiation
pressure feedback.
