A Gaia-Enceladus Analog in the EAGLE Simulation: Insights into the Early Evolution of the Milky Way

TL;DR

This study identifies a Milky Way-like galaxy in the EAGLE simulation with a similar merger history, providing insights into the galaxy's early evolution, thick disk formation, and star formation triggered by mergers.

Contribution

It presents a detailed analysis of a simulated galaxy with a Milky Way-like merger history, offering a valuable analog for understanding our galaxy's early development.

Findings

The galaxy experienced its last major merger at redshift ~1.2.

The merger contributed to thick disk formation.

The merger increased the star formation rate.

Abstract

We identify a simulated Milky Way analog in the EAGLE suite of cosmological hydrodynamical simulations. This galaxy not only shares similar global properties as the Milky Way, but was specifically selected because its merger history resembles that currently known for the Milky Way. In particular we find that this Milky Way analog has experienced its last significant merger (with a stellar mass ratio $\sim 0.2$) at $z\sim 1.2$. We show that this merger affected both the dynamical properties of the stars present at the time, contributing to the formation of a thick disk, and also leading to a significant increase in the star formation rate of the host. This object is thus particularly suitable for understanding the early evolutionary history of the Milky Way. It is also an ideal candidate for re-simulation with much higher resolution as this would allow addressing a plethora of interesting questions such as, for example, the specific distribution of dark matter near the Sun.