Mass–metallicity relation for local analogs of high-redshift galaxies: implicationsfor the evolution of the mass–metallicity relations

Abstract

We revisit the evolution of the mass–metallicity relation of low- and high-redshift galaxies by using a sample oflocal analogs of high-redshift galaxies. These analogs share the same location of the UV-selected star-forminggalaxies at~z2on the[OIII]λ5007/Hβversus[NII]λ6584/Hαnebular emission-line diagnostic(or BPT)diagram. Their physical properties closely resemble those in~z2UV-selected star-forming galaxies beingcharacterized, in particular, by high ionization parameters(»qlog7.9)and high electron densities(»-n100 cme3). With the full set of well-detected rest-frame optical diagnostic lines, we measure the gas-phase oxygen abundance in the SDSS galaxies and these local analogs using the empirical relations and thephotoionization models. Wefind that the metallicity difference between the SDSS galaxies and our local analogs inthe*<<MM8.5 log9.0()☉stellar mass bin varies from−0.09 to 0.39 dex, depending on strong-line metallicitymeasurement methods. Due to this discrepancy, the evolution of mass–metallicity should be used to compare withthe cosmological simulations with caution. We use the[SII]/Hαand[OI]/HαBPT diagram to reduce thepotential AGN and shock contamination in our local analogs. Wefind that the AGN/shock influences arenegligible on the metallicity estimation.