Twist of the Milky Way warp’s line of nodes

Determine the radial variation (twist) of the Milky Way’s warp line of nodes for the bulk stellar population, establishing whether the line of nodes forms a leading or trailing spiral as a function of galactocentric radius, and obtain a robust measurement that does not depend on sample truncation or binning choices in Gaia DR3 kinematic analyses.

Background

The authors fit kinematic models to Gaia DR3 data to infer the Milky Way’s warp properties, allowing the line of nodes and precession rate to vary with radius. Robustness tests using different radial cuts and annuli produce conflicting trends (leading vs. trailing spirals), yielding inconsistent determinations of the twist.

Given these inconsistencies across subsamples, the paper concludes that the present analysis cannot securely determine how the line of nodes varies with radius. This uncertainty persists despite clear evidence that the kinematically inferred line of nodes leads the line of nodes inferred from stellar positions.