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

Abstract

We present the first fully calibrated H${}_2$, 1-0 S(1) image of the entire 30 Doradus nebula. The observations were conducted using the NOAO Extremely Wide-Field Infrared Imager on the CTIO 4-meter Blanco Telescope. Together with a NEWFIRM Br${\hat{I}}^3$ image of 30 Doradus, our data reveal the morphologies of the warm molecular gas and ionized gas in 30 Doradus. The brightest H${}_2$-emitting area, which extends from the northeast to the southwest of R136, is a photodissociation region viewed face-on, while many clumps and pillar features located at the outer shells of 30 Doradus are photodissociation regions viewed edge-on. Based on the morphologies of H${}_2$, Br${\hat{I}}^3$, ${}^{12}$CO, and 8$\hat{I}¼$m emission, the H${}_2$ to Br${\hat{I}}^3$ line ratio and Cloudy models, we find that the H${}_2$ emission is formed inside the photodissociation regions of 30 Doradus, 2 - 3 pc to the ionization front of the HII region, in a relatively low-density environment $<$ 10${}^4$ cm${}^{-3}$. Comparisons with Br${\hat{I}}^3$, 8$\hat{I}¼$m, and CO emission indicate that H${}_2$ emission is due to fluorescence, and provide no evidence for shock excited emission of this line.

10 pages, 6 figures, 2 tables; accepted for publication in ApJ