A Model for Star Formation, Gas Flows and Chemical Evolution in Galaxies at High Redshifts

TL;DR

This paper develops an analytical model linking star formation, gas inflows and outflows, and chemical evolution in high-redshift galaxies, aligning well with observations of star formation rates and metallicities at z~2-3.

Contribution

It introduces a simple analytical framework that connects gas accretion, star formation, and chemical evolution in high-redshift galaxies, consistent with recent observations.

Findings

High star formation rates at z~2-3 require significant gas accretion.

Gas inflow rates approximately match combined star formation and outflow rates.

The model reproduces the observed mass-metallicity relation at z~2.

Abstract

Motivated by the increasing use of the Kennicutt-Schmidt (K-S) star formation law to interpret observations of high redshift galaxies, the importance of gas accretion to galaxy formation, and the recent observations of chemical abundances in galaxies at z~2-3, I use simple analytical models to assess the consistency of these processes of galaxy evolution with observations and with each other. I derive the time dependence of star formation implied by the K-S law, and show that the sustained high star formation rates observed in galaxies at z~2-3 require the accretion of additional gas. A model in which the gas accretion rate is approximately equal to the combined star formation and outflow rates broadly reproduces the observed trends of star formation rate with galaxy age. Using an analytical description of chemical evolution, I also show that this model, further constrained to have an outflow rate roughly equal to the star formation rate, reproduces the observed mass-metallicity relation at z~2.