A CONSISTENT STUDY OF METALLICITY EVOLUTION AT 0.8 < z < 2.6

Abstract

We present the correlations between stellar mass, star formation rate (SFR), and the [N-II]/H alpha flux ratio as an indicator of gas-phase metallicity for a sample of 222 galaxies at 0.8 < z < 2.6 and log(M-*/M-circle dot) = 9.0-11.5 from the LUCI, SINS/zC-SINF, and KMOS3D surveys. This sample provides a unique analysis of the mass-metallicity relation (MZR) over an extended redshift range using consistent data analysis techniques and a uniform strong-line metallicity indicator. We find a constant slope at the low-mass end of the relation and can fully describe its redshift evolution through the evolution of the characteristic turnover mass where the relation begins to flatten at the asymptotic metallicity. At a fixed mass and redshift, our data do not show a correlation between the [N-II]/H alpha ratio and SFR, which disagrees with the 0.2-0.3 dex offset in [N-II]/H alpha predicted by the "fundamental relation" between stellar mass, SFR, and metallicity discussed in recent literature. However, the overall evolution toward lower [N-II]/H alpha at earlier times does broadly agree with these predictions.