Abstract
We compute photo-ionization models for the giant extragalactic H II region NGC 2363, and compare them with optical observational data. We focus on the following observational constraints: F(Hβ), Ne, EW(Hβ), and the ratios of I(λ 5007), I(λ 4363), I(λ 3727), I(λ 6300), I(λ 6720) and I(λ 4686) relative to I(Hβ). We discuss the variations of the emission spectra obtained with different input parameters. We show that low metallicity models (Z = 0.10Z⊙) cannot reproduce the observed features of the spectrum, and that the disagreement can be satisfactorily overcome by allowing for spatial temperature fluctuations in the nebula. Accordingly, we show that the metallicity of NGC 2363 has most probably been underestimated, and that a value of Z ≃ 0.25 Z⊙ is in better agreement with the observational data than the usually adopted value Z≃0.10Z⊙. We also derive values for the slope and the high mass end of the IMF, as well as the age of the stellar cluster.
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