The SOMA Atomic Outflow Survey. I. An Atomic O I and Highly Ionized O III Outflow from Massive Protostar G11.94-00.62

Journal article, 2026

Massive stars regulate galaxy evolution and star formation through their physical and chemical feedback, but their formation remains poorly understood. Accretion-powered outflows provide important diagnostics of massive star formation. We present first results from the SOMA Atomic Outflow Survey, a far-infrared massive star formation survey using the FIFI-LS instrument on SOFIA. We report the detection of [O iii] 3P2 -> 3P1 emission at 52 mu m from the massive protostar G11.94-0.62, tracing highly ionized gas. We also detect [O i] 3P2 -> 3P1 and 3P1 -> 3P0 at 63 and 145 mu m tracing atomic gas, as well as CO J = 14 -> 13 at 186 mu m from highly excited molecular gas. The [O iii] and [O i] lines exhibit large line widths (similar to 200 and similar to 40-80 km s-1, respectively) and their morphologies are consistent with a wide-angle bipolar outflow. The properties of molecular tracers (12CO, 13CO, C18O, H2CO, and CH3OH) observed with the Atacama Large Millimeter/submillimeter Array support this interpretation. Ionized nebula and photodissociation region modeling imply an ionized outflow mass flux of similar to 8 & times; 10-5 M circle dot yr-1 and an atomic outflow mass flux of similar to 5 & times; 10-6 M circle dot yr-1, while the molecular outflow traced by CO has an implied mass flux of similar to 3 & times; 10-4 M circle dot yr-1. The mass and momentum flux in the ionized outflow are consistent with the primary disk wind, while the molecular component is mainly swept-up, secondary outflow gas. We also observe G11.94-0.62 with the Large Binocular Telescope in the near-infrared, potentially tracing the base of wide-angle outflow cavities. Spectral energy distribution modeling implies a protostellar mass m*=22.4-11+21M circle dot , while the [O iii] emission implies m* greater than or similar to 30 M circle dot and that the protostar is in the final stages of its accretion.