VIOLENT STAR-FORMATION IN NGC-2363

We present narrowband Ha imaging and long-slit optical and near-infrar ed spectroscopy of the giant H II region NGC 2363. The spectroscopic d ata are taken at two positions, in the brightest core and in a knot si milar to 6'' to the east, where we have found broad emission lines at 4660 Angstrom and 5810 Angstrom attributed to WC stars which suggest a n age for the region between 3 and 5 Myr. The observations also confir m 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 condition s and the chemical abundance of oxygen, nitrogen, neon, sulfur, and he lium. 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 Pasch en discontinuity have been obtained for two different regions. These P aschen temperatures are significantly smaller than those obtained from the collisionally excited emission line diagnostics, suggesting the p resence of large temperature fluctuations. The effect of these tempera ture fluctuations in the determination of the chemical abundances has been estimated.