# Radial phase spirals in the Solar neighbourhood

**Authors:** Jason A. S. Hunt, Adrian M. Price-Whelan, Kathryn V. Johnston, Rachel L. McClure, Carrie Filion, Ben Cassese, Danny Horta  
**arXiv:** [2401.08748](https://arxiv.org/abs/2401.08748)  
**Date:** 2024-01-16  
**Summary page:** https://www.summarizepaper.com/en/paper/2401.08748v1/

## Key points

- Second data release of ESA's Gaia mission provides insights into Milky Way's disc dynamics
- Signs of disequilibrium in the disc, particularly in kinematics of stars
- Ridges and ripples observed in planar kinematics (R-v_phi phase space)
- Prominent spiral observed in z-v_z phase space
- Study investigates equivalent phase spiral in Delta R-v_R phase space
- Models validated using observational data from Gaia Data Release 3 (DR3)
- Partial Delta R-v_R phase spirals identified in Solar neighborhood
- Suggests ongoing radial phase mixing within Galactic disc due to recent perturbations
- Future work should focus on modeling z-v_z and Delta R-v_R phase spirals simultaneously
- Contributes to understanding dynamics and evolution of galaxy's disc
- Highlights importance of considering various kinematic features when studying galactic dynamics

## Summary

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The second data release of ESA's Gaia mission has provided valuable insights into the dynamics of the Milky Way's disc. This release has revealed various signs of disequilibrium in the disc, particularly in the kinematics of stars. These signs appear as ridges and ripples in the planar kinematics, specifically in the R-v_phi phase space, and as a prominent spiral in the z-v_z phase space. In this study, the authors investigate a different aspect of these disequilibria by examining an equivalent phase spiral in the Delta R-v_R phase space. They demonstrate how this spiral forms following a perturbation to the disc using both a toy model and a high-resolution N-body simulation of a satellite interaction. To validate their models, they compare them with observational data from Gaia Data Release 3 (DR3). By analyzing this data, they identify partial Delta R-v_R phase spirals in the Solar neighborhood. This finding suggests ongoing radial phase mixing within the Galactic disc, indicating a history of recent perturbations that could arise from internal or external processes such as satellite interactions. The authors propose that future work should focus on modeling both the z-v_z and Delta R-v_R phase spirals simultaneously. Doing so may help distinguish between different possible origins of these perturbations and break any degeneracies that exist. Overall, this study contributes to our understanding of the dynamics and evolution of our galaxy's disc by investigating signatures of disequilibrium and radial phase mixing. The findings highlight the importance of considering various kinematic features when studying galactic dynamics and provide valuable insights for future research in this field.