# An intuitive 3D map of the Galactic warp's precession traced by classical Cepheids

## TL;DR

This paper uses classical Cepheids to create an accurate 3D model of the Milky Way's warp, revealing its orientation, spiral pattern, and relation to the gas disk, thus improving understanding of Galactic structure.

## Contribution

It presents the first detailed 3D Galactic warp model based on Cepheids, showing the warp's orientation, spiral pattern, and consistency with gas disk morphology.

## Key findings

- Warp's line of nodes is offset from the Galactic Center-Sun line.
- The warp exhibits a leading spiral pattern consistent with Briggs' rule.
- The stellar disk extends to at least 20 kpc, matching the gas disk morphology.

## Abstract

The Milky Way's neutral hydrogen (HI) disk is warped and flared. However, a dearth of accurate HI-based distances has thus far prevented the development of an accurate Galactic disk model. Moreover, the extent to which our Galaxy's stellar and gas disk morphologies are mutually consistent is also unclear. Classical Cepheids, primary distance indicators with distance accuracies of 3-5%, offer a unique opportunity to develop an intuitive and accurate three-dimensional picture. Here, we establish a robust Galactic disk model based on 1339 classical Cepheids. We provide strong evidence that the warp's line of nodes is not oriented in the Galactic Center-Sun direction. Instead, it subtends a mean angle of 17.5 \pm 1 (formal) \pm 3 (systematic) and exhibits a leading spiral pattern. Our Galaxy thus follows Briggs' rule for spiral galaxies, which suggests that the origin of the warp is associated with torques forced by the massive inner disk. The stellar disk traced by Cepheids follows the gas disk in terms of their amplitudes; the stellar disk extends to at least 20 kpc. This morphology provides a crucial, updated map for studies of the kinematics and archaeology of the Galactic disk.