  Radiation pressure on dust is an important feedback process around star
clusters and may eject gas from bright sub-regions in star-forming galaxies.
The Eddington ratio has previously been constructed for galaxy-averaged
observations, individual star clusters, and Galactic HII regions. Here we
assess the role of radiation pressure in thousands of sub-regions across two
local star-forming galaxies, NGC 6946 and NGC 5194. Using a model for the
spectral energy distribution from stellar population synthesis and realistic
dust grain scattering and absorption, we compute flux- and radiation
pressure-mean opacities and population-averaged optical depth $\langle\tau_{\rm
RP}\rangle$. Using Monte-Carlo calculations, we assess the momentum coupling
through a dusty column to the stellar continuum. Optically-thin regions around
young stellar populations are $30-50$ times super-Eddington. We calculate the
Eddington ratio for the sub-regions including the local mass of young and old
stars and HI and molecular gas. We compute the fraction of the total star
formation that is currently super-Eddington, and provide an assessment of the
role of radiation pressure in the dusty gas dynamics. Depending on the assumed
height of the dusty gas and the age of the stellar population, we find that
$\sim0-10$% of the sightlines are super-Eddington. These regions may be
accelerated to $\sim5-15$ km/s by radiation pressure alone. Additionally, our
results show that for beamed radiation the function $1-\exp(-\langle\tau_{\rm
RP}\rangle)$ is an excellent approximation to the momentum transfer. Opacities
and optical depths are tabulated for SEDs of different stellar ages and for
continuous star formation.
