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

TL;DR

This study uses SOFIA FEEDBACK observations to analyze the physical conditions, energy transfer, and feedback effects of massive stars in the Eagle Nebula, revealing cavity structures, gas dynamics, and energy escape mechanisms.

Contribution

It provides the first detailed characterization of the feedback processes and gas conditions in M16 using high-resolution [C II] and molecular line data.

Findings

Winds from NGC 6611 created a 20 pc cavity with most wind energy escaping.

Detected expanding shells indicating active feedback and gas dynamics.

Dense gas reservoirs remain near the cluster despite energetic feedback.

Abstract

We characterize the physical conditions and energy budget of the M16 H II region using SOFIA FEEDBACK observations of the [C II] 158 $\mu$m line. The O stars in the $\sim 10^{4}~{\rm M}_{\odot}$ NGC 6611 cluster powering this H II region have blown at least 2 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 towards N19, and traces of a thin, fragmented expanding shell towards M16. Our [C II] observations are resolved to 0.5 km s$^{-1}$ and 15.5$^{\prime\prime}$ 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 $\sim$10 K molecular gas, $10^{4}$ K photoionized gas, and million-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 $\lesssim 10^{4}~{\rm M}_{\odot}$ shell. Reservoirs of dense gas remain within a few parsecs of the cluster. N19, younger than M16 by $\gtrsim 10^6$ yr, is driven by a combination of mechanical wind energy and thermal pressure from photoionized gas and has swept up $\sim 10^{3}~{\rm M}_{\odot}$ into neutral atomic and molecular shells.