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Abstract We present ∼10–40μm SOFIA-FORCAST images of 11isolatedprotostars as part of the SOFIA Massive (SOMA) Star Formation Survey, with this morphological classification based on 37μm imaging. We develop an automated method to define source aperture size using the gradient of its background-subtracted enclosed flux and apply this to build spectral energy distributions (SEDs). We fit the SEDs with radiative transfer models, developed within the framework of turbulent core accretion (TCA) theory, to estimate key protostellar properties. Here, we release the sedcreator python package that carries out these methods. The SEDs are generally well fitted by the TCA models, from which we infer initial core massesMcranging from 20–430M⊙, clump mass surface densities Σcl∼ 0.3–1.7 g cm−2, and current protostellar massesm*∼ 3–50M⊙. From a uniform analysis of the 40 sources in the full SOMA survey to date, we find that massive protostars form across a wide range of clump mass surface density environments, placing constraints on theories that predict a minimum threshold Σclfor massive star formation. However, the upper end of them*−Σcldistribution follows trends predicted by models of internal protostellar feedback that find greater star formation efficiency in higher Σclconditions. We also investigate protostellar far-IR variability by comparison with IRAS data, finding no significant variation over an ∼40 yr baseline.
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This content will become publicly available on June 3, 2026
The SOFIA Massive (SOMA) Star Formation Survey. V. Clustered Protostars
Abstract We present ∼8–40μm 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, Σcl, and current protostellar mass,m*. We also carry out empirical graybody (GB) estimation of Σcl, which allows a case of restricted SED fitting within the TCA model grid. We also release version 2.0 of the open-source Python packagesedcreator, 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 ofMc∼ 30–200M⊙, Σcl,SED∼ 0.1–3 g cm−2, andm*∼ 4–50M⊙. The GB fitting yields smaller values of Σcl,GB≲ 1 g cm−2. From these results, we do not find evidence for a critical Σclneeded to form massive (≳8M⊙) stars. However, we do find tentative evidence for a dearth of the most massive (m*≳ 30M⊙) protostars in the clustered regions, suggesting a potential impact of environment on the stellar initial mass function.
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- Award ID(s):
- 2206437
- PAR ID:
- 10642481
- Publisher / Repository:
- Inst. of Physics
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 986
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 15
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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