The FMOS-COSMOS survey of star-forming galaxies at z~1.6. IV: Excitation state and chemical enrichment of the interstellar medium

Understand

We investigate the physical conditions of ionized gas in high-z star-forming galaxies using diagnostic diagrams based on the rest-frame optical emission lines.

• The sample consists of 701 galaxies with an Ha detection at $1.4\lesssim z\lesssim1.7$, from the FMOS-COSMOS survey, that represent the normal star-forming population over the stellar mass range $10^{9.6} \lesssim M_\ast/M_\odot \lesssim 10^{11.6}$ with those at $M_\ast>10^{11}~M_\odot$ being well sampled.
• We confirm an offset of the average location of star-forming galaxies in the BPT diagram ([OIII]/Hb vs.
• [NII]/Ha), primarily towards higher [OIII]/Hb, compared with local galaxies.