A Tilted Dark Halo Origin of the Galactic Disk Warp and Flare

TL;DR

This paper proposes that a tilted dark matter halo aligned with the stellar halo can explain the Milky Way's disk warp and flare, matching observations and offering insights into the Galaxy's formation history.

Contribution

It introduces a model where a tilted dark matter halo causes the warp and flare, quantitatively matching observational data and linking halo tilt to the Galaxy's evolution.

Findings

Dark halo tilt can produce observed warp and flare.

Warp affects both gas and stars across ages.

Galaxy's tilt provides clues to its formation history.

Abstract

The outer disk of the Milky Way Galaxy is warped and flared. Several mechanisms have been proposed to explain these phenomena, but none have quantitatively reproduced both features. Recent work has demonstrated that the Galactic stellar halo is tilted with respect to the disk plane, suggesting that at least some component of the dark matter halo may also be tilted. Here we show that a dark halo tilted in the same direction as the stellar halo can induce a warp and flare in the Galactic disk at the same amplitude and orientation as the data. In our model the warp is visible in both the gas and stars of all ages, which is consistent with the breadth of observational tracers of the warp. These results, in combination with data in the stellar halo, provide compelling evidence that our Galaxy is embedded in a tilted dark matter halo. This misalignment of the dark halo and the disk holds clue to the formation history of the Galaxy, and represents the next step in the dynamical modeling of the Galactic potential.