Exploring the Galactic Warp Through Asymmetries in the Kinematics of the Galactic Disk

Abstract

Previous analyses of large databases of Milky Way stars have revealed the stellar disk of our Galaxy to be warped and that this imparts a strong signature on the kinematics of stars beyond the solar neighborhood. However, due to the limitation of accurate distance estimates, many attempts to explore the extent of these Galactic features have generally been restricted to a volume near the Sun. By combining Gaia DR2 astrometric solution, StarHorse distance and stellar abundances from the APOGEE survey, we present the most detailed and radially expansive study yet of the vertical and radial motions of stars in the Galactic disk. We map stellar velocity with respect to their Galactocentric radius, angular momentum, and azimuthal angle and assess their relation to the warp. A decrease in vertical velocity is discovered at Galactocentric radius $R=13\text{kpc}$ and angular momentum $L_z=2800\text{kpc}\text{km}{\text{s}}^{-1}$. Smaller ripples in vertical and radial velocity are also discovered superposed on the main trend. We also discovered that trends in the vertical velocity with azimuthal angle are not symmetric about the peak, suggesting the warp to be lopsided. To explain the global trend in vertical velocity, we built a simple analytical model of the Galactic warp. Our best fit yields a starting radius of $8.87_{-0.09}^{+0.08}\text{kpc}$ and precession rate of $13.57_{-0.18}^{+0.20}\text{km}{\text{s}}^{-1}{\text{kpc}}^{-1}$. These parameters remain consistent across stellar age groups, a result that supports the notion that the warp is the result of an external, gravitationally induced phenomenon.

Accepted for publication in ApJ

References in corpus (21)

• The Gaia mission
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• galpy: A Python Library for Galactic Dynamics
• APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South
• Dynamical modelling of the Galactic bulge and bar: the Milky Way's bar pattern speed, stellar, and dark matter mass distribution
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE) Spectrographs
• The Vertical Structure of the Outer Milky Way HI Disk
• New H-band Stellar Spectral Libraries for the SDSS-III/APOGEE survey
• Bending and Breathing Modes of the Galactic Disk
• An intuitive 3D map of the Galactic warp's precession traced by classical Cepheids
• Age velocity dispersion relations and heating histories in disc galaxies
• A Magellanic Origin for the Warp of the Galaxy
• Exploring Halo Substructure with Giant Stars: The Nature of the Triangulum-Andromeda Stellar Features
• Mapping the Galactic disk with the LAMOST and Gaia Red clump sample. VI: An evidence for the long lived non-steady warp of non-gravitational scenarios
• Vertical velocities from proper motions of red clump giants
• Gaia-DR2 extended kinematical maps. Part II: Dynamics in the Galactic disk explaining radial and vertical velocities
• Parameters of the Local Warp of the Stellar-Gaseous Galactic Disk from the Kinematics of Tycho-2 Nearby Red Giant Clump Stars
• Ripple patterns in in-plane velocities of OB stars from LAMOST and Gaia
• Near-infrared and optical observations of galactic warps: A common, unexplained feature of most discs
• Mapping the Galactic disk with the LAMOST and Gaia red clump sample: IV: the kinematic signature of the Galactic warp
• Triangulum-Andromeda overdensity: a region with a complex stellar population

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• A Holistic Review of a Galactic Interaction
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• Warped Disk Galaxies. I. Linking U type Warps in Groups/Clusters to Jellyfish Galaxies
• 3-D kinematics of classical Cepheids according to Gaia, EDR3 catalog
• GaiaUnlimited: The old stellar disc of the Milky Way as traced by the Red Clump
• Topography of the Young Galactic Disk: Spatial and Kinematic Patterns of the Clustered Star Formation in the Solar Neighborhood
• Three-Dimensional Kinematics of Classical Cepheids
• RR Lyrae stars trace the Milky Way warp
• Chemodynamical Ages of Small-Scale Kinematic Structures of the Galactic Disc in the Solar Neighborhood from ~250,000 K and M Dwarfs
• Warps induced by satellites on barred and non-barred galaxies
• Azimuthal Misalignments in Stellar Warp Structure as Dynamical Tracers of Mergers in Milky Way-like Galaxies
• Modeling the vertical distribution of the Milky Way's flat subsystem objects
• Bending Waves in Velocity Space: a First Look at the THINGS sample
• No memory of past warps in the vertical density structure of galaxies
• The disturbed outer Milky Way disc