paper

The Chemical Composition of the 30 Doradus Nebula Derived from VLT Echelle Spectrophotometry

arXiv:astro-ph/0208502 · doi:10.1086/345793

Abstract

Echelle spectrophotometry of the 30 Doradus nebula in the LMC is presented. The data consists of VLT UVES observations in the 3100 to 10350 A range. The intensities of 366 emission lines have been measured, including 269 identified permitted lines of H 0, He 0, C 0, C+, N+, N++, O 0, O+, Ne 0, Ne+, S+, S++, Si 0 , Si+, Si++, Ar+, and Mg+. 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 t^2 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 HII regions. The values of Delta Y / Delta O, Delta Y / Delta Z, and Yp are also discussed.

37 pages, 2 figures, submitted to the Astrophysical Journal

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