The Milky Way’s neutral hydrogen (H i) disk is warped and flared1,2. However, a dearth of accurate H i-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% (ref. 3), offer a unique opportunity to develop an intuitive and accurate three-dimensional picture. Here, we establish a robust Galactic Disk model based on 1,339 classical Cepheids. We provide strong evidence that the warp’s line of nodes is not oriented in the Galactic Centre–Sun direction. Instead, it subtends a mean angle of 17.5° ± 1° (formal) ± 3° (systematic) and exhibits a leading spiral pattern. Our Galaxy thus follows Briggs’ rule for spiral galaxies4, which suggests that the origin of the warp is associated with torques forced by the massive inner disk5. The stellar disk traced by Cepheids follows the gas disk in terms of their amplitudes; the stellar disk extends to at least 20 kpc (refs. 6,7). This morphology provides a crucial, updated map for studies of the kinematics and archaeology of the Galactic Disk.
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The full data set of our Cepheid sample is available in Supplementary Data 1. In general, the data supporting the plots in this paper and other findings of this study are available from the corresponding author upon reasonable request.
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We are grateful for research support from the National Key Basic Research Program of China 2014CB845700. This work is also supported by the National Natural Science Foundation of China through grants U1631102, 11373010 and 11633005, the Initiative Postdocs Support Program (No. BX201600002), the China Postdoctoral Science Foundation (grant 2017M610998) and the National Key Research and Development Program of China (grant 2017YFA0402702).
The authors declare no competing interests.
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Chen, X., Wang, S., Deng, L. et al. An intuitive 3D map of the Galactic warp’s precession traced by classical Cepheids. Nat Astron 3, 320–325 (2019). https://doi.org/10.1038/s41550-018-0686-7
Nature Astronomy (2020)