Radiation Transfer of Models of Massive Star Formation. I. Dependence on
  Basic Core Properties
  Radiative transfer calculations of massive star formation are presented.
These are based on the Turbulent Core Model of McKee & Tan and
self-consistently included a hydrostatic core, an inside-out expansion wave, a
zone of free-falling rotating collapse, wide-angle dust-free outflow cavities,
an active accretion disk, and a massive protostar. For the first time for such
models, an optically thick inner gas disk extends inside the dust destruction
front. This is important to conserve the accretion energy naturally and for its
shielding effect on the outer region of the disk and envelope. The simulation
of radiation transfer is performed with the Monte Carlo code of Whitney,
yielding spectral energy distributions (SEDs) for the model series, from the
simplest spherical model to the fiducial one, with the above components each
added step-by-step. Images are also presented in different wavebands of various
telescope cameras, including Spitzer IRAC and MIPS, SOFIA FORCAST and Herschel
PACS and SPIRE. The existence of the optically thick inner disk produces higher
optical wavelength fluxes but reduces near- and mid-IR emission. The presence
of outflow cavities, the inclination angle to the line of sight, and the
thickness of the disk all affect the SEDs and images significantly. For the
high mass surface density cores considered here, the mid-IR emission can be
dominated by the outflow cavity walls, as has been suggested by De Buizer. The
effect of varying the pressure of the environment bounding the surface of the
massive core is also studied. With lower surface pressures, the core is larger,
has lower extinction and accretion rates, and the observed mid-IR flux from the
disk can then be relatively high even though the accretion luminosity is lower.
In this case the silicate absorption feature becomes prominent, in contrast to
higher density cores forming under higher pressures.
