  Forming stars emit a substantial amount of radiation into their natal
environment. We use ORION, an adaptive mesh refinement (AMR) three-dimensional
gravito-radiation-hydrodynamics code, to simulate low-mass star formation in a
turbulent molecular cloud. We compare the distribution of stellar masses,
accretion rates, and temperatures in the cases with and without radiative
transfer, and we demonstrate that radiative feedback has a profound effect on
accretion, multiplicity, and mass by reducing the number of stars formed and
the total rate at which gas turns into stars. We also show, that once star
formation reaches a steady state, protostellar radiation is by far the dominant
source of energy in the simulation, exceeding viscous dissipation and
compressional heating by at least an order of magnitude. Calculations that omit
radiative feedback from protstars significantly underestimate the gas
temperature and the strength of this effect. Although heating from protostars
is mainly confined to the protostellar cores, we find that it is sufficient to
suppress disk fragmentation that would otherwise result in very low-mass
companions or brown dwarfs. We demonstrate that the mean protostellar accretion
rate increases with the final stellar mass so that the star formation time is
only a weak function of mass.
