Structure and Feedback in 30 Doradus I: Observations

TL;DR

This study provides detailed optical imaging and spectrophotometry of 30 Doradus, revealing that photoionization by massive stars dominates over shocks in shaping the nebula, with publicly available data products.

Contribution

First comprehensive optical survey of 30 Doradus with detailed maps and catalogs, demonstrating the dominance of photoionization over shocks in nebular shaping.

Findings

Shocks are not a significant current ionization source.

Photoionization from massive stars explains nebular features.

Integrated light at cosmological distances would be dominated by low-brightness regions.

Abstract

We have completed a a new optical imaging and spectrophotometric survey of a 140 x 80 pc$^2$ region of 30 Doradus centered on R136, covering key optical diagnostic emission lines including \Ha, \Hb, \Hg, [O III] $\lambda\lambda$4363, 4959, 5007, [N II] $\lambda\lambda$6548, 6584, [S II] $\lambda\lambda$6717, 6731 [S III] $\lambda $6312 and in some locations [S III] $\lambda$9069. We present maps of fluxes and intensity ratios for these lines, and catalogs of isolated ionizing stars, elephant-trunk pillars, and edge-on ionization fronts. The final science-quality spectroscopic data products are available to the public. Our analysis of the new data finds that, while stellar winds and supernovae undoubtedly produce shocks and are responsible for shaping the nebula, there are no global spectral signatures to indicate that shocks are currently an important source of ionization. We conclude that the considerable region covered by our survey is well described by photoionization from the central cluster where the ionizing continuum is dominated by the most massive O stars. We show that if 30 Dor were viewed at a cosmological distance, its integrated light would be dominated by its extensive regions of lower surface-brightness rather than by the bright, eye-catching arcs.