W51 IRS 2: A Massive Jet Emerging from a Molecular Cloud into an H II Region

We have mapped [Ne II] (12.8 μm) and [S IV] (10.5 μm) emission from W51 IRS 2 with TEXES on Gemini North, and we compare these data to VLA free-free observations and VLT near-infrared images. With 0.5'' spatial and 4 km s-1 spectral resolution, we are able to separate the ionized gas into several components: an extended H II region on the front surface of the molecular cloud, several embedded compact H II regions, and a streamer of high-velocity gas. We interpret the high-velocity streamer as a precessing or fanlike jet, which has emerged from the molecular cloud into an OB star cluster where it is being ionized.