# 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/fr/paper/2401.08748v1/

## Abstract

The second data release of ESA's $Gaia$ mission revealed numerous signatures of disequilibrium in the Milky Way's disc. These signatures are seen in the planar kinematics of stars, which manifest as ridges and ripples in $R-v_{\phi}$, and in vertical kinematics, where a prominent spiral is seen in the $z-v_z$ phase space. In this work, we show an equivalent $\Delta R-v_{\mathrm{R}}$ phase spiral forms following a perturbation to the disc. We demonstrate the behaviour of the $\Delta R-v_{\mathrm{R}}$ phase spirals in both a toy model and a high resolution $N$-body simulation of a satellite interaction. We then confront these models with the data, where we find partial $\Delta R-v_{\mathrm{R}}$ phase spirals in the Solar neighborhood using the most recent data from $Gaia$ DR3. This structure indicates ongoing radial phase mixing in the Galactic disc, suggesting a history of recent perturbations, either through internal or external (e.g., satellite) processes. Future work modelling the $z-v_z$ and $\Delta R-v_{\mathrm{R}}$ phase spirals in tandem may help break degeneracy's between possible origins of the perturbation.