Origin of the Milky Way’s warp

Ascertain the dominant physical mechanism responsible for the Milky Way’s stellar disk warp by discriminating among proposed explanations, including torque from disk–halo misalignment, accretion of intergalactic material onto the disk, internal amplification of a misalignment between the inner and outer disk, and interactions with the Large Magellanic Cloud or the Sagittarius dwarf galaxy.

Background

Warps are common in spiral galaxies, but the Milky Way’s warp shows rapid prograde precession that challenges standard tilted-ring expectations. Multiple mechanisms have been proposed to explain the warp, and improved constraints on its structure and kinematics are needed to test these theories.

This paper measures kinematic properties of the warp and highlights tensions between kinematics and density-based warp determinations, emphasizing the need to identify the underlying cause to reconcile observations.