Winding, Unwinding, Rewinding the Gaia Phase Spiral

TL;DR

This paper summarizes the discussions and current understanding of the Gaia Phase Spiral, a stellar motion pattern revealing the Galactic disk's non-equilibrium state, based on a workshop held at Lorentz Center.

Contribution

It compiles recent knowledge, open questions, and community resources regarding the Gaia Phase Spiral, fostering collaborative efforts to understand its origin and physics.

Findings

The Gaia Phase Spiral indicates the Galactic disk is out of equilibrium.

Workshop discussions identified key open questions in the field.

Resources and projects were shared to advance research on the Phase Spiral.

Abstract

The Gaia Space Satellite has transformed the field of Galactic Dynamics by collecting 6D phase space information for hundreds of millions of stars. In 2018, it enabled the discovery of the Gaia Phase Spiral (Antoja et al., 2018), a clear signal in the vertical motion of the stars that reveals how far from equilibrium the Galactic disk is. Seven years after the discovery of this structure, a workshop dedicated to the Phase Spiral took place at the Lorentz Center. Workshop participants summarized the current state of knowledge about the Phase Spiral and identified open questions and key areas to continue progressing in understanding the origin of the Phase Spiral and the physics governing the response of the disk to perturbations. Here, we aim to summarize the content and discussions of this workshop, share the resources that have been produced at this workshop with the broader community, and invite interested individuals to join on the projects that started.