The SOFIA Massive (SOMA) Star Formation Survey. II. High Luminosity
  Protostars
  We present multi-wavelength images observed with SOFIA-FORCAST from $\sim$10
to 40 $\mu$m of seven high luminosity massive protostars, as part of the SOFIA
Massive (SOMA) Star Formation Survey. Source morphologies at these wavelengths
appear to be influenced by outflow cavities and extinction from dense gas
surrounding the protostars. Using these images, we build spectral energy
distributions (SEDs) of the protostars, also including archival data from
Spitzer, Herschel and other facilities. Radiative transfer (RT) models of Zhang
& Tan (2018), based on Turbulent Core Accretion theory, are then fit to the
SEDs to estimate key properties of the protostars. Considering the best five
models fit to each source, the protostars have masses $m_{*} \sim 12-64 \:
M_{\odot}$ accreting at rates of $\dot{m}_{*} \sim 10^{-4}-10^{-3} \: M_{\odot}
\: \rm yr^{-1}$ inside cores of initial masses $M_{c} \sim 100-500 \:
M_{\odot}$ embedded in clumps with mass surface densities $\Sigma_{\rm cl} \sim
0.1-3 \: \rm g \: cm^{-2}$ and span a luminosity range of $10^{4} -10^{6} \:
L_{\odot}$. Compared with the first eight protostars in Paper I, the sources
analyzed here are more luminous, and thus likely to be more massive protostars.
They are often in a clustered environment or have a companion protostar
relatively nearby. From the range of parameter space of the models, we do not
see any evidence that $\Sigma_{\rm cl}$ needs to be high to form these massive
stars. For most sources the RT models provide reasonable fits to the SEDs,
though the cold clump material often influences the long wavelength fitting.
However, for sources in very clustered environments, the model SEDs may not be
such a good description of the data, indicating potential limitations of the
models for these regions.
