What hydrodynamical simulations tell us about the radial properties of the stellar populations in Ellipticals

TL;DR

This study uses hydrodynamical simulations with detailed chemical evolution to explore the formation and radial metallicity variations in elliptical galaxies, successfully reproducing key observed relations and gradients.

Contribution

Introduces a new gas dynamical model that reproduces metallicity, color-magnitude, and [alpha/Fe] gradients in elliptical galaxies, revealing outside-in formation.

Findings

Galaxies form outside-in with rapid outer gas accretion and star formation.

Model reproduces observed mass-metallicity and color-magnitude relations.

Radial [alpha/Fe] gradients can be positive or negative, matching observations.

Abstract

Elliptical galaxies probably host the most metal rich stellar populations in the Universe. The processes leading to both the formation and the evolution of such stars are discussed by means of a new gas dynamical model which implements detailed chemical evolution prescriptions. Moreover, the radial variations in the metallicity distribution of these stars are investigated by means of G-dwarf-like diagrams. By comparing model predictions with observations, we derive a picture of galaxy formation in which the higher is the mass of the galaxy, the shorter are the infall and the star formation timescales. The galaxies seem to have formed outside-in, namely the most external regions accrete gas, form stars and develop a galactic wind very quickly (a few Myr) compared to the central core, where the star formation can last up to 1 Gyr. We show for the first time a model able in reproducing the mass-metallicity and the color-magnitude relations as well as the radial metallicity gradient, and, at the same time, the observed either positive or negative slopes in the [alpha/Fe] abundace ratio gradient in stars.