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We use the second Gaia data release in combination with the catalog ofSanders & Das (2018) to dissect the Milky Way disc in phase-space and relativeages. We confirm and report the existence of multiple velocity moving groups atlow azimuthal velocities and angular momenta, below Arcturus, regularlyseparated by $\sim~18-20\,\rm{km s^{-1}}$ in azimuthal velocity. Such featureswere predicted to exist more than ten years ago from the reaction of the MilkyWay to a perturbation in the disc undergoing phase-mixing. These structuresappear slightly younger than their phase-space surroundings, arguing against anextra-galactic origin. We also identify in relative age many of the classicalridges in the plane of azimuthal velocity vs. Galactocentric radius,traditionally associated with resonance features. These ridges are also youngerthan their phase-space surroundings in accordance with predictions from recentstate-of-the-art cosmological hydrodynamical simulations of Milky Way-likegalaxies. We study the response of dynamically young and old stellar discpopulations to resonances from an analytic model of a large bar, which,remarkably, qualitatively reproduces the trends seen in the data. Our resultsre-inforce the idea that the Galactic disc is currently being shaped by bothinternal and external perturbations, and that, while absolute isochrone ageshave to be taken with great care, exploring the dynamical structure of the discin stellar ages, especially with future asteroseismic data, will provide muchstronger constraints than metallicity/abundance trends alone.

The bar resonances and low angular momentum moving groups in the Galaxy revealed by stellar ages