On the oxygen abundance determination in H bt II regions. The problem of the line intensities - oxygen abundance calibration

The problem of the line intensities - oxygen abundance calibration has been considered. We confirm the idea of McGaugh (1991) that the strong oxygen lines ([OII] lambda lambda 3727, 3729 and [OIII] lambda lambda 4959, 5007) contain the necessary information for determination of accurate abundances in low-metallicity (and may be also in high-metallicity) H ii regions. It has been found that the excitation parameters p₃ or p₂ (which are defined here as contributions of the radiation in [OIII] lambda lambda 4959, 5007 lines and in [OII] lambda lambda 3727, 3729 lines to the ``total" oxygen radiation respectively) allow to take into account the variations in R₂₃ values among H ii regions with a given oxygen abundance. Based on this fact a new way of the oxygen abundance determination in H ii regions (p - method) has been constructed and corresponding relations between [OII] lambda lambda 3727, 3729, [OIII] lambda lambda 4959, 5007 line intensities and the oxygen abundance have been derived empirically using the available oxygen abundances determined via measurement of temperature-sensitive line ratios (T_e - method). In parallel a new R₂₃ calibration has been derived on the base of recent data and compared to previous calibrations. For oxygen-rich H ii regions the present R₂₃ calibration is close to that of Edmunds & Pagel (1984): their calibration has the same slope but is shifted towards higher oxygen abundances by around 0.07 dex as compared to the present calibration.