Metallicity Calibrations and the Mass‐Metallicity Relation for Star‐forming Galaxies

We investigate the effect of metallicity calibrations, AGN classification, and aperture covering fraction on the local mass-metallicity (M-Z) relation using 27,730 star-forming galaxies from the SDSS Data Release 4. We analyze the SDSS M-Z relation with 10 metallicity calibrations, including theoretical and empirical methods. We show that the choice of metallicity calibration has a significant effect on the shape and y-intercept [12 + log (O/H)] of the M-Z relation. The absolute metallicity scale (y-intercept) varies up to Δ [log (O/H)] = 0.7 dex, depending on the calibration used, and the change in shape is substantial. These results indicate that it is critical to use the same metallicity calibration when…