ChemZz I: Comparing Oxygen and Iron Abundance Patterns in the Milky Way, the Local Group and Cosmic Noon

Stephanie Monty; Allison L. Strom; Thomas M. Stanton; Martyna Chruślińska; Fergus Cullen; Chiaki Kobayashi; Tjitske Starkenburg; Souradeep Bhattacharya; Jason L. Sanders; Mark Gieles

arXiv · 2507.14094

ChemZz I: Comparing Oxygen and Iron Abundance Patterns in the Milky Way, the Local Group and Cosmic Noon

Stephanie Monty·Allison L. Strom·Thomas M. Stanton·Martyna Chruślińska·Fergus Cullen·Chiaki Kobayashi·Tjitske Starkenburg·Souradeep Bhattacharya·Jason L. Sanders·Mark Gieles

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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 ($z{\sim}2-3$) 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 $\alpha$- and iron-enhancement trends with mass in the $z{\sim}2-3$ galaxies and find good agreement between these galaxies and the MW high-$\alpha$ disc in [O/Fe] vs. [Fe/H]. We also find excellent agreement between the [O/Fe] trends seen in the MW high- and low-$\alpha$ discs with O-abundances seen in old and young planetary nebulae in M~31 respectively, supporting the existence of $\alpha$-bimodality in the inner regions of M~31. Finally, we use globular cluster ages to project the MW and GSE back in time to $z{\sim}3$ and find that their estimated mass, oxygen and iron abundances are strikingly consistent with the mass-metallicity relation of star-forming galaxies at $z{\sim}3$. 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.

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Stephanie Monty, Allison L. Strom, Thomas M. Stanton, Martyna Chruślińska, Fergus Cullen, Chiaki Kobayashi, Tjitske Starkenburg, Souradeep Bhattacharya, Jason L. Sanders, Mark Gieles. 2025-07-18. ChemZz I: Comparing Oxygen and Iron Abundance Patterns in the Milky Way, the Local Group and Cosmic Noon. https://arxiv.org/abs/2507.14094

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