The MZ relation for local star-forming galaxies

We investigate the evolution of the mass-metallicity (MZ) relation with a large sample of 53,444 star-forming galaxies (SFGs) at $0.04<z<0.12$, selected from the catalog of MPA-JHU emission-line measurements for the Sloan Digital Sky Survey (SDSS) Data Release 7. Regarding the sample of SFGs, we correct the observational bias and raise the aperture covering fractions to check the reliability of the metallicity evolution. We show that (1) the redshift evolution of log($\rm H\alpha$) and log(O III) luminosities is displayed in our sample; (2) we find the metallicity evolution of $\sim 0.15$ dex at $\rm log (M_*/M_\odot)\sim9.3$ in SFGs at $0.04<z<0.12$; (3) after applying the luminosity thresholds of log$(L_{\rm H \alpha})>41.0$ and log$(L_{\rm O\ III})>39.7$, we find that metallicity evolution is shown well, and that SFR evolution still is shown well under the latter luminosity threshold, but the evolution is not observed under the former one; (4) the evolution of the MZ relation seems to disappear at about $\rm log(M_{*}/M_\odot)>10.0$ after applying the luminosity threshold of log$(L_{\rm H \alpha})>41.0$ or log$(L_{\rm O\ III})>39.7$; (5) we find $\alpha =0.09$ and $\alpha =0.07$ in the equation ($\mu={\rm log}M_{*}-\alpha \rm log(SFR)$) for log$(L_{\rm H \alpha})>41.0$ and log$(L_{\rm O\ III})>39.7$ samples, respectively, and these imply that the evolution of the MZ relation may have a weaker dependence on SFR in our sample.