Simulations of high-redshift [OIII] emitters: Chemical evolution and multi-line diagnostics

TL;DR

This study uses high-resolution galaxy simulations to analyze the chemical evolution and multi-line diagnostics of high-redshift [OIII] emitters, providing insights into their physical conditions and line emission properties.

Contribution

It introduces a physical model for HII regions in simulations, linking line emission to galaxy evolution and enabling diagnostics of high-redshift galaxy interstellar medium.

Findings

Massive galaxies rapidly chemically evolve by z=9.

Young stellar populations enhance [OIII] line emission.

Line flux ratios can estimate gas density and metallicity.

Abstract

Recent observations by James Webb Space Telescope discovered a number of high-redshift galaxies with strong emission lines from doubly ionized oxygen. Combined with ALMA observations of far-infrared lines, multi-line diagnostics can be applied to the high-redshift galaxies in order to probe the physical conditions of the inter-stellar 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 HII regions and calculate spatially resolved [OIII] 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 [OIII] 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 [OIII] emitters.