A Case against a Significant Detection of Precession in the Galactic Warp

Abstract

Recent studies of warp kinematics using Gaia DR2 data have produced detections of warp precession for the first time, which greatly exceeds theoretical predictions of models. However, this detection assumes a warp model derived for a young population (few tens of megayears) to fit velocities of an average older stellar population of the thin disk (several gigayears) in Gaia-DR2 observations, which may lead to unaccounted systematic errors. Here, we recalculate the warp precession with the same approach and Gaia DR2 kinematic data, but using different warp parameters based on the fit of star counts of the Gaia DR2 sample, which has a much lower warp amplitude than the young population. When we take into account this variation of the warp amplitude with the age of the population, we find that there is no need for precession. We find the value of warp precession $\beta =4_{-4}^{+6}$ km s${}^{-1}$ kpc${}^{-1}$, which does not exclude nonprecessing warp.

12 pages, 8 figures, accepted to be published in ApJ

References in corpus (10)

• The Gaia mission
• Outer structure of the Galactic warp and flare: explaining the Canis Major over-density
• An intuitive 3D map of the Galactic warp's precession traced by classical Cepheids
• Revised Geometric Estimates of the North Galactic Pole and the Sun's Height Above the Galactic Midplane
• Formation of Warped Disks by Galactic Fly-by Encounters. I. Stellar Disks
• 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
• Exploring the pertubed Milky Way disk and the substructures of the outer disk
• 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
• Structure of the outer Galactic disc with Gaia-DR2

Cited by in corpus (12)

• Tracing the Milky Way warp and spiral arms with classical Cepheids
• The Flare and Warp of the Young Stellar Disk traced with LAMOST DR5 OB-type stars
• A twisted and precessing Cepheid warp in the outer Milky Way disc
• Warp and flare of the old Galactic disc as traced by the red clump stars
• The Great Wave: Evidence of a large-scale vertical corrugation propagating outwards in the Galactic disc
• The tangled warp of the Milky Way
• A slightly oblate dark matter halo revealed by a retrograde precessing Galactic disk warp
• Evidence for Populations-dependent vertical motions and the Long-lived Non-Steady Lopsided Milky Way Warp
• 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
• Three-Dimensional Kinematics of Classical Cepheids
• Modeling the vertical distribution of the Milky Way's flat subsystem objects