We search for the maximum oxygen abundance in spiral galaxies .
Because this maximum value is expected to occur in the centers of the most luminous galaxies , we have constructed the luminosity – central metallicity diagram for spiral galaxies , based on a large compilation of existing data on oxygen abundances of H ii regions in spiral galaxies .
We found that this diagram shows a plateau at high luminosities ( -22.3 \la M _ { B } \la -20.3 ) , with a constant maximum value of the gas-phase oxygen abundance 12+log ( O/H ) \sim 8.87 .
This provides strong evidence that the oxygen abundance in the centers of the most luminous metal-rich galaxies reaches the maximum attainable value of oxygen abundance .
Since some fraction of the oxygen ( about 0.08 dex ) is expected to be locked into dust grains , the maximum value of the true gas+dust oxygen abundance in spiral galaxies is 12+log ( O/H ) \sim 8.95 .
This value is a factor of \sim 2 higher than the recently estimated solar value .
Based on the derived maximum oxygen abundance in galaxies , we found the oxygen yield to be about 0.0035 , depending on the fraction of oxygen incorporated into dust grains .