Oxygen abundances in dwarf irregular galaxies and the metallicity-luminosity relationship

The low-luminosity dwarf irregular galaxies are considered. The oxygen abundances in H II regions of dwarf irregular galaxies were recalculated from published spectra through the recently suggested P-method. It has been found that the metallicity of low-luminosity dwarf irregular galaxies, with a few exceptions, correlates well with galaxy luminosity. The dispersion of oxygen abundances around the metallicity-luminosity relationship increases with decreasing galaxy luminosity, as was found by Richer & McCall (1995). The absence of a relationship between the oxygen abundance and the absolute magnitude in the blue band for irregular galaxies obtained by Hidalgo-Gamez & Olofsson (1998) can be explained by the large uncertainties in the oxygen abundances derived through the T-e-method, that in turn can be explained by the large uncertainties in the measurements of the strengths of the weak oxygen line [OIII]lambda 4363 used in the T-e-method.