# Signatures of resonance and phase mixing in the Galactic disc

## TL;DR

This paper analyzes Gaia DR2 star kinematics to identify signatures of resonance and phase mixing in the Galactic disc, demonstrating how transient spiral structures and the bar influence local stellar motions.

## Contribution

It introduces a combined model of bar and spiral structures in action-angle space that reproduces observed kinematic features in Gaia data.

## Key findings

- Phase mixing from transient spirals creates ridges and arches in local kinematics.
- A bar with various pattern speeds, combined with spirals, qualitatively matches Gaia observations.
- Decoupling bar and spiral effects remains challenging.

## Abstract

Gaia DR2 has provided an unprecedented wealth of information about the kinematics of stars in the Solar neighbourhood, and has highlighted the degree of features in the Galactic disc. We confront the data with a range of bar and spiral models in both action-angle space, and the $R_{\mathrm{G}}-v_{\phi}$ plane. We find that the phase mixing induced by transient spiral structure creates ridges and arches in the local kinematics which are consistent with the Gaia data. We are able to produce a qualitatively good match to the data when combined with a bar with a variety of pattern speeds, and show that it is non trivial to decouple the effects of the bar and the spiral structure.