# The SOFIA Massive (SOMA) Star Formation Survey. II. High Luminosity Protostars

## TL;DR

This study uses multi-wavelength observations and radiative transfer modeling to analyze high-luminosity massive protostars, revealing their properties, environments, and potential formation conditions within the Turbulent Core Accretion framework.

## Contribution

It provides detailed SED fitting and property estimates for high-mass protostars, expanding understanding of their formation and environment, especially in clustered regions.

## Key findings

- Protostars have masses 12-64 M_sun and luminosities 10^4-10^6 L_sun.
- Models fit most SEDs well, but clustering affects long-wavelength fits.
- No strong evidence that high surface density is necessary for massive star formation.

## Abstract

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.