The SOFIA Massive (SOMA) Star Formation Survey and the open-source python package sedcreator

Massive stars have dramatic impacts throughout the universe at different scales and are one of the reasons you are reading this abstract today. But their birth, deep within dusty molecular clouds, is literally shrouded in uncertainty. The formation of massive protostars is still an open question and there is still a lot to be understood. Theories range from Core Accretion, i.e., a scaled-up version of low-mass star formation, to Competitive Accretion at the crowed centres of forming star clusters, to Stellar Collisions. The SOMA survey aims at understanding the basic formation mechanisms governing massive stellar birth through multi-wavelength observations but also through radiative transfer (RT) modelling of their spectral energy distributions (SEDs).

Here I present the current status of the SOFIA Massive (SOMA) Star Formation Survey for which more than 40 sources have been observed in the mid-infrared with SOFIA/FORCAST and that have been combined with Spitzer and Herschel observations. These data were used to construct SEDs and to fit a grid of RT models. To do this, we used the open-source python package sedcreator which is also presented to the community. This package includes a number of convenient tools to measure fluxes on any astronomical image and to fit to a set of models. We find evidence that relatively massive protostars can form across a range of clump mass surface density environments, which contradicts some models for the required conditions of massive star formation. However, we see a trend that to form the most massive protostars, i.e., $m_*> 25 M_\odot$, the mass surface density $(\Sigma_\mathrm{cl})$ needs to be $>1\,\mathrm{g\,cm^{-2}}$. Our favoured explanation for this result is the Turbulent Core Accretion model prediction that the star formation efficiency of a core due to internal protostellar feedback is higher in higher $\Sigma_\mathrm{cl}$ environments.