Mass-Metallicity Relation for Local Analogs of High-Redshift galaxies: Implications for the Evolution of the Mass-Metallicity Relations

TL;DR

This study investigates the mass-metallicity relation of local galaxy analogs to high-redshift galaxies, revealing discrepancies in metallicity measurements and emphasizing cautious comparison with cosmological simulations.

Contribution

It provides a detailed analysis of metallicity differences using various measurement methods and assesses contamination effects, enhancing understanding of galaxy evolution.

Findings

Metallicity difference varies from -0.09 to 0.39 dex in certain mass bins.

Discrepancies depend on strong-line metallicity measurement methods.

AGN and shock contamination are negligible for metallicity estimates.

Abstract

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 $z\sim2$ on the [OIII]/H$\beta$ versus [NII]/H$\alpha$ nebular emission-line diagnostic (or BPT) diagram. Their physical properties closely resemble those in $z\sim2$ UV-selected star-forming galaxies being characterized in particular by high ionization parameters ($\log q\approx7.9$) and high electron densities ($n_e\approx100~\rm{cm}^{-3}$). 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 the photoionization models. We find that the metallicity difference between the SDSS galaxies and our local analogs in the $8.5<log(M_*/M_{\odot})<9.0$ 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 [SII]/H$\alpha$ and [OI]/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.