The Subaru FMOS Galaxy Redshift Survey (FastSound): The Mass-Metallicity Relation and the Fundamental Metallicity Relation at z ~ 1.4

摘要

We present results from a large NIR spectroscopic survey (FastSound) with Subaru/FMOS, consisting of ~4,000 galaxies at z ~ 1.4 with significant Ha detection. The resulting mass-metallicity relation generally agrees with those obtained previously in a similar redshift range to our sample. No clear dependence on the mass-metallicity relation on star-formation rate is found, which is not in agreement with the extrapolation of the local fundamental metallicity relation. We estimate the nitrogen-to-oxygen abundance ratio (N/O) from the N2S2 index, and find that the N/O in galaxies at z ~ 1.4 is significantly higher than the local values at a fixed metallicity and stellar mass. The metallicity derived by using the N2 method calibrated in the local universe decreases by ~ 0.2 dex if we correct the N/O enhancement.