Molecular Gas in the Eagle Nebula

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Abstract
We present the first images of the molecular gas in the Eagle Nebula. Our maps of 12CO (1-0),13CO (1-0), and 12C18O (1-0) emission, which have about 10'' (~0.1 pc) resolution, reveal a molecular cloud being demolished by the intense activity of nearby O stars. Velocity gradients in the molecular gas reach up to 20 km s-1 pc-1—enormous in comparison to typical clouds—with position angles that point directly back to the O stars. We infer the three-dimensional structure of the cloud from its kinematic and illumination patterns. We derive the physical conditions of the molecular gas and compare them with those in the ionized layer surrounding the cloud. The derived gas pressure is high, P/k~108 cm−3 K, and the ionized and neutral phases appear to be in pressure equilibrium. We show that the cloud's large "elephant trunks" are unlikely to have arisen as a result of a Rayleigh-Taylor instability. From the data, we measure directly the evaporation and dynamic timescales of the cloud. The former is much longer than the lifetime of the O stars, while the latter is much shorter and therefore more important to the cloud's ultimate fate. Morphological features in the CO images correspond in detail to those in images from the Hubble Space Telescope.

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