The SOFIA Massive (SOMA) Star Formation Survey. V. Clustered Protostars

Journal article, 2025

We present similar to 8-40 mu m SOFIA-FORCAST images of seven regions of "clustered" star formation as part of the SOFIA Massive Star Formation Survey. We identify a total of 34 protostar candidates and build their spectral energy distributions (SEDs). We fit these SEDs with a grid of radiative transfer models based on the turbulent core accretion (TCA) theory to derive key protostellar properties, including initial core mass, Mc, clump environment mass surface density, Sigma cl, and current protostellar mass, m*. We also carry out empirical graybody (GB) estimation of Sigma cl, which allows a case of restricted SED fitting within the TCA model grid. We also release version 2.0 of the open-source Python package sedcreator, which is designed to automate the aperture photometry and SED building and fitting process for sources in clustered environments, where flux contamination from close neighbors typically complicates the process. Using these updated methods, SED fitting yields values of Mc similar to 30-200 M circle dot, Sigma cl,SED similar to 0.1-3 g cm-2, and m* similar to 4-50 M circle dot. The GB fitting yields smaller values of Sigma cl,GB less than or similar to 1 g cm-2. From these results, we do not find evidence for a critical Sigma cl needed to form massive (greater than or similar to 8 M circle dot) stars. However, we do find tentative evidence for a dearth of the most massive (m* greater than or similar to 30 M circle dot) protostars in the clustered regions, suggesting a potential impact of environment on the stellar initial mass function.