ChemZz I: comparing oxygen and iron abundance patterns in the Milky Way, the Local Group, and Cosmic Noon

Abstract

Our understanding of the chemical evolution of galaxies has advanced through measurements from both distant galaxies across redshift, and our own Milky Way (MW). To form a comprehensive picture, it is essential to unify these constraints, placing them on a common scale and parlance and to understand their systematic differences. In this study, we homogenize oxygen and iron measurements from star-forming galaxies at Cosmic Noon (z∼2–3) with resolved stellar abundances from the Local Group. The MW is divided into four components, assuming the outer halo is dominated by debris from the Gaia-Sausage-Enceladus (GSE) progenitor. After converting all abundances to a common solar scale, we identify clear α- and iron-enhancement trends with mass in the z∼2–3 galaxies and find good agreement between these galaxies and the MW high-α disc in [O/Fe] versus [Fe/H]. We also find excellent agreement between the [O/Fe] trends seen in the MW high- and low-α discs with O-abundances seen in old and young planetary nebulae in M 31 respectively, supporting the existence of α-bimodality in the inner regions of M 31. Finally, we use globular cluster ages to project the MW and GSE back in time to z∼3 and find that their estimated mass, oxygen and iron abundances are strikingly consistent with the mass–metallicity relation of star-forming galaxies at z∼3. In the future, increased transparency around the choice of solar scale and abundance methodology will make combining chemical abundances easier – contributing to a complete picture of the chemical evolution of all galaxies.