2003ApJ...584..735P

Echelle spectrophotometry of the 30 Doradus nebula in the LMC is presented. The data consist of VLT UVES observations in the 3100-10350 Å range. The intensities of 366 emission lines have been measured, including 269 identified permitted lines of H⁰, He⁰, C⁰, C⁺, N⁺, N⁺⁺, O⁰, O⁺, Ne⁰, Ne⁺, S⁺, S⁺⁺, Si⁰, Si⁺, Si⁺⁺, Ar⁺, and Mg⁺; many of them are produced by recombination only while others mainly by fluorescence. Electron temperatures and densities have been determined using different line intensity ratios. The He⁺, C⁺⁺, O⁺, and O⁺⁺ ionic abundances have been derived from recombination lines; these abundances are almost independent of the temperature structure of the nebula. Alternatively, abundances from collisionally excited lines have been derived for a large number of ions of different elements; these abundances depend strongly on the temperature structure. Accurate t² values have been derived from the Balmer continuum and by comparing the C⁺⁺, O⁺, and O⁺⁺ ionic abundances obtained from collisionally excited and recombination lines. The chemical composition of 30 Doradus is compared with those of Galactic and extragalactic H II regions. The values of ΔY/ΔO, ΔY/ΔZ, and Y_pare also discussed.