Molecular and Ionized Hydrogen in 30 Doradus. I. Imaging Observations

We present the first fully calibrated H₂ 1-0 S(1) image of the entire 30 Doradus nebula. The observations were conducted using the NOAO Extremely Wide-field Infrared Imager (NEWFIRM) on the CTIO 4 m Blanco Telescope. Together with a NEWFIRM Brγ image of 30 Doradus, our data reveal the morphologies of the warm molecular gas and ionized gas in 30 Doradus. The brightest H₂-emitting area, which extends from the northeast to the southwest of R136, is a photodissociation region (PDR) viewed face-on, while many clumps and pillar features located at the outer shells of 30 Doradus are PDRs viewed edge-on. Based on the morphologies of H₂, Brγ, CO, and 8 μm emission, the H₂ to Brγ line ratio, and Cloudy models, we find that the H₂ emission is formed inside the PDRs of 30 Doradus, 2-3 pc to the ionization front of the H ii region, in a relatively low-density environment <10⁴ cm^-3. Comparisons with Brγ, 8 μm, and CO emission indicate that H₂ emission is due to fluorescence, and provide no evidence for shock excited emission of this line.