In section 6. Interstellar and circumstellar matter
Anatomy of the massive star-forming region S106. The OI 63 micron line observed with GREAT/SOFIA as a versatile diagnostic tool for the evolution of massive stars
The star-forming region S106 has been an object of intense interest for decades as a model region for studying massive star formation. These new spectroscopic observations, performed with GREAT/SOFIA have superb spatial (3 arcsec stepping, about 500 AU) and velocity (about 0.04 km/s) resolutions. They are supplemented with IRAM mm and archival VLA cm and Herschel IR imaging to produce a comprehensive, virtually tomographic, picture of the region. Particularly lovely is the association of different parts of the [O I] profile with structures in the cm radio imaging. The way in which the [O I] precisely traces the ionised gas (from cm observations) in the low velocity interval of the line profiles. The paper highlights how high spectral resolution and multiple tracers provide the three-dimensional ionization, density, and velocity structure, even distinguishing between shock and radiative excitations. This paper serves as a model analysis for future observational programs on spatially resolved star forming regions.