The Chemical Evolution of Dwarf Spheroidal Galaxies: Dissecting the Inner Regions and their Stellar Populations

TL;DR

This study uses 3D hydrodynamical simulations to analyze the chemical and kinematic properties of dwarf spheroidal galaxies' inner regions, revealing distinct stellar populations shaped by supernovae types and inhomogeneous pollution.

Contribution

It provides a novel simulation-based analysis of chemical evolution and stellar population segregation in dwarf spheroidal galaxies, emphasizing the roles of SNe Ia and SNe II.

Findings

Inner regions show inhomogeneous pollution from SNe Ia.

Metal-rich stars are centrally segregated and alpha-element-depleted.

An anti-correlation exists between [Fe/H] and velocity dispersion.

Abstract

Using 3-dimensional hydrodynamical simulations of isolated dwarf spheroidal galaxies (dSphs), we undertake an analysis of the chemical properties of their inner regions, identifying the respective roles played by Type Ia (SNe Ia) and Type II (SNe II) supernovae. The effect of inhomogeneous pollution from SNe Ia is shown to be prominent within two core radii, with the stars forming therein amounting to ~20% of the total. These stars are relatively iron-rich and alpha-element-depleted compared to the stars forming in the rest of the galaxy. At odds with the projected stellar velocity dispersion radial profile, the actual 3-dimensional one shows a depression in the central region, where the most metal-rich (ie. [Fe/H]-rich) stars are partly segregated. This naturally results in two different stellar populations, with an anti-correlation between [Fe/H] and velocity dispersion, in the same sense as that observed in the Sculptor and Fornax dSphs. Because the most iron-rich stars in our model are also the most alpha-depleted, a natural prediction and test of our model is that the same radial segregation effects should exist between [alpha/Fe] and velocity dispersion.