Oxygen and nitrogen abundances in nearby galaxies

We performed a compilation of more than 1000 published spectra of H ii regions in spiral galaxies. The oxygen and nitrogen abundances in each H ii region were recomputed in a homogeneous way, using the P-method. The radial distributions of oxygen and nitrogen abundances were derived. The correlations between oxygen abundance and macroscopic properties are examined. We found that the oxygen abundance in spiral galaxies correlates with its luminosity, rotation velocity, and morphological type: the correlation with the rotation velocity may be slightly tighter. There is a significant difference between the luminosity–metallicity relationship obtained here and that based on the oxygen abundances determined through the R23-calibrations. The oxygen abundance of NGC 5457 recently determined using direct measurements of Te (Kennicutt et al. [CITE]) agrees with the luminosity–metallicity relationship derived in this paper, but is in conflict with the luminosity–metallicity relationship derived with the R23-based oxygen abundances. The obtained luminosity–metallicity relation for spiral galaxies is compared to that for irregular galaxies. Our sample of galaxies shows evidence that the slope of the relationship for spirals () is slightly more shallow than that for irregular galaxies (). The effective oxygen yields were estimated for spiral and irregular galaxies. The effective oxygen yield increases with increasing luminosity from to (or with increasing rotation velocity from km s-1 to km s-1) and then remains approximately constant. Irregular galaxies from our sample have effective oxygen yields lowered by a factor of 3 at maximum, i.e. irregular galaxies usually keep at least 1/3 of the oxygen they manufactured during their evolution.