Mapping Milky Way disk perturbations in stellar number density and vertical velocity using Gaia DR3

Abstract

We have mapped the number density and mean vertical velocity of the Milky Way's stellar disk out to roughly two kiloparsecs from the Sun using Gaia Data Release 3 (DR3) and complementary photo-astrometric distance information from StarHorse. For the number counts, we carefully masked spatial regions that are compromised by open clusters, great distances, or dust extinction and used Gaussian processes to arrive at a smooth, non-parametric estimate for the underlying number density field. We find that the number density and velocity fields depart significantly from an axisymmetric and mirror-symmetric model. These departures, which include projections of the Gaia phase-space spiral, signal the presence of local disturbances in the disk. We identify two features that are present in both stellar number density and mean vertical velocity. One of these features appears to be associated with the Local Spiral Arm. It is most prominent at small heights and is largely symmetric across the mid-plane of the disk. The density and velocity field perturbations are phase-shifted by roughly a quarter wavelength, suggesting a breathing mode that is propagating in the direction of Galactic longitude $l\sim 270$ deg. The second feature is a gradient in the stellar number density and mean vertical velocity with respect to Galactocentric radius. This feature, which extends across the entire region of our analysis, may be associated with the extension of the Galactic warp into the Solar neighbourhood in combination with more localised bending waves.

13 pages, 11 figures, appendices add 12 pages, 11 figures; accepted for publication in A&A

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• Growing Local arm inferred by the breathing motion
• First spiral arm detection using dynamical mass measurements of the Milky Way disk
• The missing radial velocities of Gaia: a catalogue of Bayesian estimates for DR3
• Polarization Properties of the Electromagnetic Response to High-frequency Gravitational Wave
• Two-point correlation function studies for the Milky Way: discovery of spatial clustering from disk excitations and substructure
• A Wave-Corrected Assessment of the Local Midplane
• Correlation between the two-armed $V_R$ spiral in the $Z$--$V_Z$ plane and moving groups