Study of star-forming galaxies in SDSS up to redshift 0.4: I. Metallicity evolution

TL;DR

This study investigates the evolution of gas-phase metallicity in star-forming galaxies at low redshifts (0.04 to 0.4) using SDSS data, revealing a modest decrease in metallicity over this period.

Contribution

It provides the first detailed analysis of metallicity evolution in massive star-forming galaxies at low redshift, linking local and high-redshift galaxy evolution.

Findings

Metallicity decreases by ~0.1 dex from redshift 0 to 0.4.

Significant evolution observed in the mass-metallicity relation.

No strong bias from fiber size effects detected.

Abstract

The chemical composition of the gas in galaxies versus cosmic time provides a very important tool for understanding galaxy evolution. Although there are many studies at high redshift, they are rather scarce at lower redshifts. However, low redshift studies can provide important clues about the evolution of galaxies, furnishing the required link between local and high redshift universe. In this work we focus on the metallicity of the gas of star-forming galaxies at low redshift, looking for signs of chemical evolution. To analyze the metallicity contents star-forming galaxies of similar luminosities and masses at different redshifts. With this purpose, we present a study of the metallicity of relatively massive (log(M_star/M_sun)>10.5) star forming galaxies from SDSS--DR5 (Sloan Digital Sky Survey--Data Release 5), using different redshift intervals from 0.04 to 0.4. We used data processed with the STARLIGHT spectral synthesis code, correcting the fluxes for dust extinction, estimating metallicities using the R_23 method, and segregating the samples with respect to the value of the [NII]6583/[OII]3727 line ratio in order to break the R_23 degeneracy selecting the upper branch. We analyze the luminosity and mass-metallicity relations, and the effect of the Sloan fiber diameter looking for possible biases. By dividing our redshift samples in intervals of similar magnitude and comparing them, significant signs of metallicity evolution are found. Metallicity correlates inversely with redshift: from redshift 0 to 0.4 a decrement of ~0.1 dex in 12+log(O/H) is found.