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

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

Abstract

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 VRand Vz. Below the plane, we find the largest radial gradient to be ∂VR/∂R = -7.01 ± 0.61 km s-1kpc-1, in agreement with recent studies. Above the plane, we find a similar gradient with ∂VR/∂R = -9.42 ± 1.77 km s-1kpc-1. By comparing our results with previous studies, we find that the structure in Vzis 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.

Citation

Carrillo, I., Minchev, I., Kordopatis, G., Steinmetz, M., Binney, J., Anders, F., Bienaymé, O., Bland-Hawthorn, J., Famaey, B., Freeman, K. C., Gilmore, G., Gibson, B. K., Grebel, E. K., Helmi, A., Just, A., Kunder, A., McMillan, P., Monari, G., Munari, U., Navarro, J., …Zwitter, T. (2018). Is the Milky Way still breathing? RAVE–Gaia streaming motions. Monthly notices of the Royal Astronomical Society, 475(2), 2679-2696. https://doi.org/10.1093/mnras/stx3342

• Journal Article Type: Article
• Acceptance Date: Dec 24, 2017
• Online Publication Date: Jan 5, 2018
• Publication Date: Apr 1, 2018
• Deposit Date: Jun 26, 2018
• Publicly Available Date: Jun 26, 2018
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 475
• Issue: 2
• Pages: 2679-2696
• DOI: https://doi.org/10.1093/mnras/stx3342
• Keywords: Galaxy: disc; Galaxy: kinematics and dynamics; Galaxy: structure
• Public URL: https://hull-repository.worktribe.com/output/888748
• Publisher URL: https://academic.oup.com/mnras/article/475/2/2679/4791582
• Related Public URLs: https://arxiv.org/abs/1710.03763
• Contract Date: Jun 26, 2018