The Elemental Abundance Distributions of Milky Way Satellite Galaxies

TL;DR

This study analyzes the chemical compositions of stars in Milky Way satellite galaxies to understand their gas flow and star formation histories, revealing correlations between luminosity, metallicity, and supernova contributions.

Contribution

It provides a comprehensive spectroscopic survey of multiple elements in nearly 3000 stars across eight dwarf satellites, highlighting how galaxy luminosity influences chemical evolution.

Findings

More luminous galaxies are more metal-rich.

Gas infall is necessary to explain metallicity distributions.

Alpha-to-iron ratios decrease with increasing metallicity.

Abstract

The chemical compositions of the stars in Milky Way (MW) satellite galaxies reveals the history of gas flows and star formation (SF) intensity. This talk presented a Keck/DEIMOS spectroscopic survey of the Fe, Mg, Si, Ca, and Ti abundances of nearly 3000 red giants in eight MW dwarf satellites. The metallicity and alpha-to-iron ratio distributions obey the following trends: (1) The more luminous galaxies are more metal-rich, indicating that they retained gas more efficiently than the less luminous galaxies. (2) The shapes of the metallicity distributions of the more luminous galaxies require gas infall during their SF lifetimes. (3) At [Fe/H] < -1.5, [alpha/Fe] falls monotonically with increasing [Fe/H] in all MW satellites. One interpretation of these trends is that the SF timescale in any MW satellite is long enough that Type Ia supernovae exploded for nearly the entire SF lifetime.