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.Comment: 37 pages, 2 figures, submitted to the Astrophysical Journa