MASS-METALLICITY RELATION FOR LOCAL ANALOGS OF HIGH-REDSHIFT GALAXIES: IMPLICATIONS FOR THE EVOLUTION OF THE MASS-METALLICITY RELATIONS

We revisit the evolution of the mass-metallicity relation of low- and high-redshift galaxies by using a sample of local analogs of high-redshift galaxies. These analogs share the same location of the UV-selected star-forming galaxies at z similar to 2 on the [O III]lambda 5007/H beta versus [N II]lambda 6584/H alpha nebular emission-line diagnostic (or BPT) diagram. Their physical properties closely resemble those in z similar to 2 UV-selected star-forming galaxies being characterized, in particular, by high ionization parameters (log q approximate to 7.9) and high electron densities (n(e) approximate to 100 cm(-3)). With the full set of well-detected rest-frame optical diagnostic lines, we measure the gasphase oxygen abundance in the SDSS galaxies and these local analogs using the empirical relations and the photoionization models. We find that the metallicity difference between the SDSS galaxies and our local analogs in the 8.5 < log(M-* M-Theta) < 9.0 stellar mass bin varies from -0.09 to 0.39 dex, depending on strong-line metallicity measurement methods. Due to this discrepancy, the evolution of mass-metallicity should be used to compare with the cosmological simulations with caution. We use the [S II]/H alpha and [O I]/H alpha BPT diagram to reduce the potential AGN and shock contamination in our local analogs. We find that the AGN/shock influences are negligible on the metallicity estimation.