Star-forming galaxies in SDSS: signs of metallicity evolution

Evolution of galaxies through cosmic time has been widely studied at high redshift, but there are a few studies in this field at lower redshifts. However, low-redshifts studies will provide important clues to 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 in spiral galaxies at low redshift looking for signs of chemical evolution. We analyze the metallicity contents of star forming galaxies of similar luminosities at different redshifts, we studied the metallicity of star forming galaxies from SDSS-DR5 (Sloan Digital Sky Survey-Data Release 5), using different redshift intervals from 0.1 to 0.4. We used the public data of SDSS-DR5 processed with the STARLIGHT spectral synthesis code, correcting the fluxes for dust extinction, estimating metallicities using the R23 method, and analyzing the samples with respect to the [NII]6583/[OII]3727 line ratio. From a final sample of 207 galaxies, we find a decrement in 12+log(O/H) corresponding to the redshift interval 0.3 < z < 0.4 of ~0.1 dex with respect to the rest of the sample, which can be interpreted as evidence of the metallicity evolution in low-z galaxies.Comment: 4 pages, 3 figure

Metallicity estimates with SDSS-DR6

Abstract We present a study of the metallicity of 20268 galaxies from the Sloan Digital Sky Survey -Data Release 6 (SDSS-DR6) using the R 23 method, and derive analytical calibrations from several metallicity-sensitive line ratios: [ performed the study for the resdshift interval (0.04-0.1) for all the Sloan survey release. This is the first part of a more complete work which aims to study the metallicity dependances of the star-forming galaxies in the Local Unvierse