The Gaia-ESO Survey: a quiescent Milky Way with no significant dark/stellar accreted disc

TL;DR

This study uses chemo-dynamical analysis of Gaia-ESO data to investigate the Milky Way's merger history, finding no evidence of an accreted stellar or dark matter disc, indicating a quiescent evolutionary past.

Contribution

It applies a chemo-dynamical template to a large stellar sample to search for accreted components, revealing the absence of an accreted disc in the Milky Way.

Findings

Significant accreted halo stars detected

No evidence of an accreted stellar disc found

Milky Way's merger history appears quiescent since 8-10 billion years ago

Abstract

According to our current cosmological model, galaxies like the Milky Way are expected to experience many mergers over their lifetimes. The most massive of the merging galaxies will be dragged towards the disc-plane, depositing stars and dark matter into an accreted disc structure. In this work, we utilize the chemo-dynamical template developed in Ruchti et al. to hunt for accreted stars. We apply the template to a sample of 4,675 stars in the third internal data release from the Gaia-ESO Spectroscopic Survey. We find a significant component of accreted halo stars, but find no evidence of an accreted disc component. This suggests that the Milky Way has had a rather quiescent merger history since its disc formed some 8-10 billion years ago and therefore possesses no significant dark matter disc.