The fundamental metallicity relation from SDSS (z~0) to VIPERS (z~0.7) Data selection or evolution

TL;DR

This study examines how selection biases and physical evolution affect the observed fundamental metallicity relation (FMR) in galaxies from SDSS to VIPERS, emphasizing the importance of data quality and sample matching.

Contribution

It demonstrates the impact of data selection biases on FMR projections and provides a method to compare galaxy samples across different redshifts by constructing equivalent datasets.

Findings

FMR projections are sensitive to S/N and spectral quality biases.

The metallicity vs. sSFR plane is robust against these biases.

Luminosity function evolution biases the metallicity vs. SFR relation.

Abstract

Aims. We focus on how to homogenize the comparison between galaxy samples having different characteristics. We check the projections of the fundamental metallicity relation (FMR) and the evolution of these projections between a sample selected at $z\sim0$ (SDSS) and $z\sim0.7$ (VIPERS). We check, in particular, whether and to what extent selection criteria can affect the results. Methods. We checked the influence of different biases introduced either by physical constraints (evolution of the luminosity function and differences in the fraction of blue galaxies) or data selection (the signal-to-noise ratio and quality of the spectra) on the FMR and its projections. To separate the differences occurring due to the physical evolution of galaxies with redshift from the false evolution mimed by these biases, we first analyzed the effects of these biases individually on the SDSS sample, and next, starting from the SDSS data, we built a VIPERS-equivalent $z \sim 0$ sample, replicating the main characteristics of VIPERS sample at $z\sim0.7$ for a fair comparison. Results. We found that the FMR projections are all sensitive to biases introduced by the selection on S/N and the quality flags of the emission line measurements in the spectra, especially the $\left[\text{O{\,\sc{iii}}}\right]\lambda 4959$ line. The exception is the metallicity versus the sSFR plane which is insensitive to these biases. The evolution of the luminosity function introduces a bias only in the plane metallicity versus the star formation rate (SFR) while the fraction of blue galaxies has no impact on results.