VIOLENT STAR-FORMATION IN NGC-2363

We present narrowband Ha imaging and long-slit optical and near-infrared spectroscopy of the giant H II region NGC 2363. The spectroscopic data are taken at two positions, in the brightest core and in a knot similar to 6'' to the east, where we have found broad emission lines at 4660 Angstrom and 5810 Angstrom attributed to WC stars which suggest an age for the region between 3 and 5 Myr. The observations also confirm previously reported low-intensity broad components in H alpha and [O III] emission lines, which extend some 500 pc across the region. For 15 different zones within the nebula, we derive the physical conditions and the chemical abundance of oxygen, nitrogen, neon, sulfur, and helium. No significant spatial variations are found for these abundances, with a mean value of oxygen 12 + log (O/H) = 7.89 and a helium mass fraction of gamma = 0.24. Electron temperatures deduced from the Paschen discontinuity have been obtained for two different regions. These Paschen temperatures are significantly smaller than those obtained from the collisionally excited emission line diagnostics, suggesting the presence of large temperature fluctuations. The effect of these temperature fluctuations in the determination of the chemical abundances has been estimated.