# Inhomogeneous Galactic Chemical Evolution: Modelling Ultra-Faint Dwarf Galaxies of the Large Magellanic Cloud

**Authors:** Ryan K. Alexander, Fiorenzo Vincenzo, Alexander P. Ji, Hannah Richstein, Chris J. Jordan, Brad K. Gibson  
**arXiv:** [2303.12530](https://arxiv.org/abs/2303.12530)  
**Date:** 2023-03-22  
**Summary page:** https://www.summarizepaper.com/en/paper/2303.12530v1/

## Key points

- Ryan K. Alexander and colleagues present a novel inhomogeneous chemical evolution model, i-GEtool
- The model is used to study the chemical abundance dispersion in ultra-faint dwarf galaxies
- Ultra-faint dwarf galaxies are among the oldest and most metal-poor in the cosmos and contain no traces of gas at present times but have a high dark matter mass fraction
- Understanding the chemical abundance dispersion in such extreme environments could shed light on the properties of the first generations of stars in the cosmos
- The authors apply their model to two ultra-faint dwarf galaxies, Carina II (Car II) and Reticulum II (Ret II), which are satellites of the Large Magellanic Cloud
- The i-GEtool model is based on Monte Carlo sampling of the initial mass function as star formation proceeds in different gas cells of the simulated galaxy volume
- By focusing on $\alpha$- and odd-$\textit{Z}$ elements, they predict two sequences in [C/Fe] and [N/Fe] at all metallicities
- Their models systematically underestimate [C/Fe] and [Ti/Fe] due to large uncertainties in adopted stellar nucleosynthesis yields
- The authors' Supernova feedback scheme drives galactic outflows that quench star formation activity early on
- The average outflow mass-loading factor predicted by their models is $\approx 10^{3}$
- Synthetic color-magnitude diagrams were drawn for Car II and Ret II and compared with observations
- This study provides valuable insights into understanding chemical evolution of ultra-faint dwarf galaxies while also offering a useful tool for future studies in this area through its application to Carina II (Car II) and Reticulum II (Ret II).

## Summary

In their recent paper, Ryan K. Alexander and colleagues present a novel inhomogeneous chemical evolution model, i-GEtool, which they use to study the chemical abundance dispersion in ultra-faint dwarf galaxies. These galaxies are among the oldest and most metal-poor in the cosmos and contain no traces of gas at present times but have a high dark matter mass fraction. Understanding the chemical abundance dispersion in such extreme environments could shed light on the properties of the first generations of stars in the cosmos. The authors apply their model to two ultra-faint dwarf galaxies, Carina II (Car II) and Reticulum II (Ret II), which are satellites of the Large Magellanic Cloud. The i-GEtool model is based on Monte Carlo sampling of the initial mass function as star formation proceeds in different gas cells of the simulated galaxy volume. The authors account for the chemical enrichment of Supernova bubbles as they spread in the interstellar medium, causing dispersion in predicted elemental abundances. By focusing on $\alpha$- and odd-$\textit{Z}$ elements, they predict two sequences in [C/Fe] and [N/Fe] at all metallicities. However, their models systematically underestimate [C/Fe] and [Ti/Fe] due to large uncertainties in adopted stellar nucleosynthesis yields. The observed C and N abundances had likely been affected by internal mixing processes that changed initial surface abundances in red giants. The authors' Supernova feedback scheme drives galactic outflows that quench star formation activity early on. The average outflow mass-loading factor predicted by their models is $\approx 10^{3}$, extrapolating towards very low galaxy stellar masses from trends observed at high stellar masses. Finally, by combining their model with MIST isochrone database, synthetic color-magnitude diagrams were drawn for Car II and Ret II and compared with observations. Overall, this study provides valuable insights into understanding chemical evolution of ultra-faint dwarf galaxies while also offering a useful tool for future studies in this area through its application to Carina II (Car II) and Reticulum II (Ret II).