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Photo of Paul McMillan

Paul McMillan


Photo of Paul McMillan

Is the Milky Way still breathing? RAVE-Gaia streaming motions


  • I. Carrillo
  • I. Minchev
  • G. Kordopatis
  • M. Steinmetz
  • J. Binney
  • F. Anders
  • O. Bienaymé
  • J. Bland-Hawthorn
  • B. Famaey
  • K. C. Freeman
  • G. Gilmore
  • B. K. Gibson
  • E. K. Grebel
  • A. Helmi
  • A. Just
  • A. Kunder
  • P. McMillan
  • G. Monari
  • U. Munari
  • J. Navarro
  • Q. A. Parker
  • W. Reid
  • G. Seabroke
  • S. Sharma
  • A. Siebert
  • F. Watson
  • J. Wojno
  • R. F.G. Wyse
  • T. Zwitter

Summary, in English

We use data from the Radial Velocity Experiment (RAVE) and the Tycho-Gaia astrometric solution (TGAS) catalogue to compute the velocity fields yielded by the radial (VR), azimuthal (Vϕ),and vertical (Vz) components of associated Galactocentric velocity. We search in particular for variation in all three velocity components with distance above and below the disc midplane, as well as how each component of Vz (line-of-sight and tangential velocity projections) modifies the obtained vertical structure. To study the dependence of velocity on proper motion and distance, we use two main samples: a RAVE sample including proper motions from the Tycho-2, PPMXL, and UCAC4 catalogues, and a RAVE-TGAS sample with inferred distances and proper motions from the TGAS and UCAC5 catalogues. In both samples, we identify asymmetries in VR and Vz. Below the plane, we find the largest radial gradient to be ∂VR/∂R = -7.01 ± 0.61 km s-1 kpc-1, in agreement with recent studies. Above the plane, we find a similar gradient with ∂VR/∂R = -9.42 ± 1.77 km s-1 kpc-1. By comparing our results with previous studies, we find that the structure in Vz is strongly dependent on the adopted proper motions. Using the Galaxia Milky Way model, we demonstrate that distance uncertainties can create artificial wave-like patterns. In contrast to previous suggestions of a breathing mode seen in RAVE data, our results support a combination of bending and breathing modes, likely generated by a combination of external or internal and external mechanisms.


  • Lund Observatory

Publishing year







Monthly Notices of the Royal Astronomical Society





Document type

Journal article


Oxford University Press


  • Astronomy, Astrophysics and Cosmology


  • Galaxy: disc
  • Galaxy: kinematics and dynamics
  • Galaxy: structure




  • ISSN: 0035-8711