Numerical Simulations of Turbulent Molecular Clouds Regulated by
  Radiation Feedback Forces II: Radiation-Gas Interactions and Outflows
  Momentum deposition by radiation pressure from young, massive stars may help
to destroy molecular clouds and unbind stellar clusters by driving large-scale
outflows. We extend our previous numerical radiation hydrodynamic study of
turbulent, star-forming clouds to analyze the detailed interaction between
non-ionizing UV radiation and the cloud material. Our simulations trace the
evolution of gas and star particles through self-gravitating collapse, star
formation, and cloud destruction via radiation-driven outflows. These models
are idealized in that we include only radiation feedback and adopt an
isothermal equation of state. Turbulence creates a structure of dense filaments
and large holes through which radiation escapes, such that only ~50% of the
radiation is (cumulatively) absorbed by the end of star formation. The surface
density distribution of gas by mass as seen by the central cluster is roughly
lognormal with sigma_ln(Sigma) = 1.3-1.7, similar to the externally-projected
surface density distribution. This allows low surface density regions to be
driven outwards to nearly 10 times their initial escape speed v_esc. Although
the velocity distribution of outflows is broadened by the lognormal surface
density distribution, the overall efficiency of momentum injection to the gas
cloud is reduced because much of the radiation escapes. The mean outflow
velocity is approximately twice the escape speed from the initial cloud radius.
Our results are also informative for understanding galactic-scale wind driving
by radiation, in particular the relationship between velocity and surface
density for individual outflow structures, and the resulting velocity and mass
distributions arising from turbulent sources.
