Kinematic footprint of the Milky Way spiral arms in Gaia EDR3

Abstract

The Milky Way spiral arms are well established from star counts as well as from the locus of molecular clouds and other young objects, however, they have only recently started to be observed from a kinematics point of view. Using the kinematics of thin disc stars in Gaia EDR3 around the extended solar neighbourhood, we create x-y projections coloured by the radial, residual rotational, and vertical Galactocentric velocities ($U,\Delta V,W$). The maps are rich in substructures and reveal the perturbed state of the Galactic disc. We find that local differences between rotational velocity and the azimuthally averaged velocity, $\Delta V$, display at least five large-scale kinematic spirals; two of them closely follow the locus of the Sagittarius-Carina and Perseus spiral arms, with pitch angles of 9.12${}^{\circ }$ and 7.76${}^{\circ }$, and vertical thickness of $\sim 400$ pc and $\sim 600$ pc, respectively. Another kinematic spiral is located behind the Perseus arm and appears as a distortion in rotation velocities left by this massive arm but with no known counterpart in gas/stars overdensity. A weaker signal close to the Sun's position is present in our three velocity maps, and appears to be associated with the Local arm. Our analysis of the stellar velocities in the Galactic disc shows kinematic differences between arms and inter-arms, that are in favour of Milky Way spiral arms that do not corotate with the disc. Moreover, we show that the kinematic spirals are clumpy and flocculent, revealing the underlying nature of the Milky Way spiral arms.

11 pages, 6 Figures, 1 Table. Accepted for publication in MNRAS

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Cited by in corpus (14)

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• Growing Local arm inferred by the breathing motion
• Catalog of spiral arm Tangents (Galactic Longitudes) in the Milky Way, and the Age Gradient based on various arm tangents
• Parallax-based Distances to Galactic Hii Regions: Nearby Spiral Structure
• Parameters of the Galactic Spiral Density Wave from Masers with Parallax Errors Less Than 10%
• First spiral arm detection using dynamical mass measurements of the Milky Way disk
• Measuring the Streaming motion in the Milky Way disc with Gaia EDR3 +
• The Mysterious Radcliffe Wave
• Topography of the Young Galactic Disk: Spatial and Kinematic Patterns of the Clustered Star Formation in the Solar Neighborhood
• The fragility of thin discs in galaxies -- I. Building tailored N-body galaxy models
• Metal-rich stellar counterpart of the Radcliffe Wave and the 3D chemical footprints of the Milky Way spiral arms
• Signatures of simulated spiral arms on radial actions