Simulations of High-redshift [O iii] Emitters: Chemical Evolution and Multiline Diagnostics

Recent observations by the James Webb Space Telescope discovered a number of high-redshift galaxies with strong emission lines from doubly ionized oxygen. Combined with Atacama Large Millimeter/submillimeter Array observations of far-infrared lines, multiline diagnostics can be applied to the high-redshift galaxies in order to probe the physical conditions of the interstellar medium. We study the formation and evolution of galaxies using the FirstLight simulation suite, which provides outputs of 62 high-resolution, zoom-in galaxy simulations. We devise a physical model of H ii regions and calculate spatially resolved [O iii] line emission. We show that massive galaxies with stellar masses of M (*) > 10(9) M (& ODOT;) chemically evolve rapidly to z = 9. Young stellar populations in the star-forming galaxies boost the [O iii] line emission, rendering the ratio of line luminosity to star formation rate larger than that for low-redshift galaxies, which is consistent with recent observations. Measuring the flux ratios of rest-frame optical and far-infrared lines allows us to estimate the physical conditions such as density and metallicity of the star-forming gas in high-redshift [O iii] emitters.

Automated summary

Recent observations by the James Webb Space Telescope have discovered high-redshift galaxies with strong emission lines from doubly ionized oxygen. Using multiline diagnostics, combined with observations of far-infrared lines, we investigate the physical conditions of the interstellar medium in these galaxies. Our study using the FirstLight simulation suite shows that massive galaxies with stellar masses greater than 10^9 solar masses rapidly evolve chemically to z = 9. We find that young stellar populations in star-forming galaxies enhance the [O iii] line emission, resulting in higher line luminosity to star formation rate ratios compared to low-redshift galaxies.