Metal enrichment in a semi-analytical model, fundamental scaling relations, and the case of Milky Way galaxies

TL;DR

This paper extends a semi-analytical galaxy formation model to include metal enrichment, analyzing how different accretion and star formation scenarios affect metallicity evolution, especially in Milky Way-like galaxies, and compares results with observations.

Contribution

It introduces a chemodynamical extension to the eGalICS model to track metallicity from primordial to enriched gas, and evaluates different galaxy formation scenarios against observational data.

Findings

Strong star formation regulation reproduces the local mass-metallicity relation.

Models show a dependence of metallicity on star formation rate.

Milky Way progenitors evolve below the main sequence before reaching it at z=0.

Abstract

Gas flows play a fundamental role in galaxy formation and evolution, providing the fuel for the star formation process. These mechanisms leave an imprint in the amount of heavy elements. Thus, the analysis of this metallicity signature provides additional constraint on the galaxy formation scenario. We aim to discriminate between four different galaxy formation models based on two accretion scenarios and two different star formation recipes. We address the impact of a bimodal accretion scenario and a strongly regulated star formation recipe. We present a new extension of the eGalICS model, which allows us to track the metal enrichment process. Our new chemodynamical model is applicable for situations ranging from metal-free primordial accretion to very enriched interstellar gas contents. We use this new tool to predict the metallicity evolution of both the stellar populations and gas phase. We also address the evolution of the gas metallicity with the star formation rate (SFR). We then focus on a sub-sample of Milky Way-like galaxies. We compare both the cosmic stellar mass assembly and the metal enrichment process of such galaxies with observations and detailed chemical evolution models. Our models, based on a strong star formation regulation, allow us to reproduce well the stellar mass to gas-phase metallicity relation observed in the local universe. However, we observe a systematic shift towards high masses. Our $Mstar-Zg-SFR relation is in good agreement with recent measurements: our best model predicts a clear dependence with the SFR. Both SFR and metal enrichment histories of our Milky Way-like galaxies are consistent with observational measurements and detailed chemical evolution models. We finally show that Milky Way progenitors start their evolution below the observed main sequence and progressively reach this observed relation at z = 0.