A Potential Dynamical Origin of The Galactic Disk Warp: The Gaia-Sausage-Enceladus Major Merger

TL;DR

This study uses simulations of a gas-rich Gaia-Sausage-Enceladus merger to explain the origin and evolution of the Milky Way's disk warp, matching observed features and suggesting a major merger as its cause.

Contribution

It presents the first simulation of a gas-rich GSE merger that reproduces the Galactic warp's features, offering a potential dynamical origin for the warp.

Findings

Successfully reproduces observed warp features

Demonstrates a single major merger can generate warp amplitude and precession

Provides insights into the Milky Way's formation history

Abstract

Previous studies have revealed that the Galactic warp is a long-lived, nonsteady, and asymmetric structure. There is a need for a model that accounts for the warp's long-term evolution. Given that this structure has persisted for over 5 Gyrs, its timeline may coincide with the completion of Gaia-Sausage-Enceladus (GSE) merger. Recent studies indicate that the GSE, the significant merger of our Galaxy, was likely a gas-rich merger and the large amount of gas introduced could have created a profound impact on the Galactic morphology. This study utilizes GIZMO simulation code to construct a gas-rich GSE merger. By reconstructing the observed characteristics of the GSE, we successfully reproduce the disk warp and capture nearly all of its documented features that aligns closely with observational data from both stellar and gas disks. This simulation demonstrates the possibility that the single major merger could generate the Galactic warp amplitude and precession. Furthermore, the analysis of the warp's long-term evolution may offer more clues into the formation history of the Milky Way.