Radiation Transfer of Models of Massive Star Formation. IV. The Model
  Grid and Spectral Energy Distribution Fitting
  We present a continuum radiative transfer model grid for fitting observed
spectral energy distributions (SEDs) of massive protostars. The model grid is
based on the paradigm of core accretion theory for massive star formation with
pre-assembled gravitationally-bound cores as initial conditions. In particular,
following the Turbulent Core Model, initial core properties are set primarily
by their mass and the pressure of their ambient clump. We then model the
evolution of the protostar and its surround structures in a self-consistent
way. The model grid contains about 9000 SEDs with 4 free parameters: initial
core mass, the mean surface density of the environment, the protostellar mass,
and the inclination. The model grid is used to fit observed SEDs via chi^2
minimization, with the foreground extinction additionally estimated. We
demonstrate the fitting process and results using the example of massive
protostar G35.20- 0.74. Compared with other SED model grids currently used for
massive star formation studies, in our model grid, the properties of the
protostar and its surrounding structures are more physically connected, which
reduces the dimensionality of the parameter spaces and the total number of
models. This excludes possible fitting of models that are physically
unrealistic or that are not internally self-consistent in the context of the
Turbulent Core Model. Thus, this model grid serves not only as a fitting tool
to estimate properties of massive protostars, but also as a test of core
accretion theory. The SED model grid is publicly released with this paper.
