SOFIA FEEDBACK Survey: The Eagle Nebula in [C ii] and Molecular Lines

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 ∼104 M⊙ 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 .″ 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 ≲104 M⊙ 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 ∼103 M⊙ into neutral atomic and molecular shells.