2025ApJ...995..196K

We characterize the physical conditions and energy budget of the M16 H II region using Stratospheric Observatory for Infrared Astronomy FEEDBACK observations of the [C II] 158 μm line. The O stars in the ∼10⁴M_⊙ NGC 6611 cluster powering this H II region have blown at least two cavities into the giant molecular cloud: the large M16 cavity and the small N19 bubble. We detect the spectroscopic signature of an expanding photodissociation region shell toward N19, and traces of a thin, fragmented expanding shell toward M16. Our [C II] observations are resolved to 0.5 km s^–1 and 15$\mathop{.}\limits^{\unicode{x02033}}$5 and analyzed alongside similarly resolved CO J = 3-2 observations as well as archival data ranging from the radio to X-ray tracing a variety of gas phases spanning dense ∼10 K molecular gas, 10⁴ K photoionized gas, and 1,000,000 K collisionally ionized plasma. With this dataset, we evaluate the coupling of energetic feedback from NGC 6611 and the O9 V star within N19 to the surrounding gas. Winds from NGC 6611 have blown a 20 pc radius cavity constrained in size along the major axis of the natal giant molecular filament, and much of the mechanical wind energy (>90%) has escaped through breaches in the ≲10⁴M_⊙ shell. Reservoirs of dense gas remain within a few parsecs of the cluster. N19, younger than M16 by ≳10⁶ yr, is driven by a combination of mechanical wind energy and thermal pressure from photoionized gas and has swept up ∼10³M_⊙ into neutral atomic and molecular shells.