The Effect of Star Formation on the Redshift Evolution of Interstellar Metals, Atomic and Molecular Gas in Galaxies

TL;DR

This study investigates how star formation influences the evolution of interstellar gas and metals in galaxies across different redshifts, using semi-analytic models with varying prescriptions for molecular gas formation.

Contribution

It demonstrates that the star formation law affects the gas, stars, and metals balance over time but not the total stellar mass formed below redshift 2.5, providing constraints on gas conversion timescales.

Findings

Star formation law impacts gas-metal balance evolution.

Total stellar mass formed is unaffected below z~2.5.

Gas conversion timescale remains around 1-2 Gyr at high redshifts.

Abstract

We examine how the atomic and molecular gas components of galaxies evolve to higher redshifts using the semi-analytic galaxy formation models of Fu et al. (2010) in which we track the surface density profiles of gas in disks. We adopt two different prescriptions based either on gas surface density and metallicity, or on interstellar pressure, to compute the molecular fraction as a function of radius in each disk. We demonstrate that the adopted star formation law determines how the {\em balance} between gas, stars and metals changes with time in the star-forming galaxy population, but does not influence the total mass in stars formed into galaxies at redshifts below $z\sim 2.5$. The redshift evolution of the mass-metallicity relation places strong constraints on the timescale over which cold gas is converted into stars in high redshift galaxies, and favours models where this remains constant at values around 1-2 Gyr. Future observations of the evolution of the average molecular-to-atomic gas ratio in galaxies as a function of stellar mass and redshift will constrain models of the atomic-to-molecular transition.