A Census of Oxygen in Star-Forming Galaxies: An Empirical Model Linking Metallicities, Star Formation Rates and Outflows

TL;DR

This study provides an empirical analysis of oxygen content in star-forming galaxies across different redshifts, linking metallicities, star formation rates, and outflows to understand chemical evolution and baryon loss.

Contribution

It introduces a novel empirical model connecting metallicities, star formation rates, and oxygen outflows in galaxies over cosmic time.

Findings

Oxygen loss scales almost linearly with stellar mass.

Most baryons do not accrete onto galaxies, indicating significant baryon loss.

The chemical evolution of galaxies is constrained by observed mass-metallicity relations.

Abstract

In this contribution we present the first census of oxygen in star-forming galaxies in the local universe. We examine three samples of galaxies with metallicities and star formation rates at z = 0.07, 0.8 and 2.26, including the SDSS and DEEP2 surveys. We infer the total mass of oxygen produced and mass of oxygen found in the gas-phase from our local SDSS sample. The star formation history is determined by requiring that galaxies evolve along the relation between stellar mass and star formation rate observed in our three samples. We show that the observed relation between stellar mass and star formation rate for our three samples is consistent with other samples in the literature. The mass-metallicity relation is well established for our three samples and from this we empirically determine the chemical evolution of star-forming galaxies. Thus, we are able to simultaneously constrain the star formation rates and metallicities of galaxies over cosmic time allowing us to estimate the mass of oxygen locked up in stars. Combining this work with independent measurements reported in the literature we conclude that the loss of oxygen from the interstellar medium of local star-forming galaxies is likely to be a ubiquitous process with the oxygen mass loss scaling (almost) linearly with stellar mass. We estimate the total baryonic mass loss and argue that only a small fraction of the baryons inferred from cosmological observations accrete onto galaxies.