Hic sunt dracones: Cartography of the Milky Way spiral arms and bar resonances with Gaia Data Release 2

Abstract

In this paper we introduce a new method for analysing Milky Way phase-space which allows us to reveal the imprint left by the Milky Way bar and spiral arms on the stars with full phase-space data in Gaia Data Release 2. The unprecedented quality and extended spatial coverage of these data enable us to discover six prominent stellar density structures in the disc to a distance of 5 kpc from the Sun. Four of these structures correspond to the spiral arms detected previously in the gas and young stars (Scutum-Centaurus, Sagittarius, Local and Perseus). The remaining two are associated with the main resonances of the Milky Way bar where corotation is placed at around 6.2 kpc and the outer Lindblad resonance beyond the Solar radius, at around 9 kpc. For the first time we provide evidence of the imprint left by spiral arms and resonances in the stellar densities not relying on a specific tracer, through enhancing the signatures left by these asymmetries. Our method offers new avenues for studying how the stellar populations in our Galaxy are shaped.

10 pages, 6 figures, accepted for publication in A&A Letters

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• Mass models of the Milky Way and estimation of its mass from the GAIA DR3 data-set
• The spiral structure in the Solar neighborhood
• Evidence of a vertical kinematic oscillation beyond the Radcliffe Wave
• Local Spiral Structure Traced by Red Clump Stars
• The power of co-ordinate transformations in dynamical interpretations of Galactic structure
• A low density-wave spiral pattern speed, from the tracer separations (age gradient) across a spiral arm in the Milky Way
• Impact of bar resonances in the velocity-space distribution of the solar neighbourhood stars in a self-consistent $N$-body Galactic disc simulation
• Axial Asymmetry Studies in Gaia Data Release 2 Yield the Pattern Speed of the Galactic Bar
• Arm Tangents and the spiral structure of the Milky Way ; the Age Gradient
• Tracing Milky Way substructure with an RR Lyrae hierarchical clustering forest
• Distance and extinction to the Milky Way spiral arms along the Galactic centre line of sight