The large-scale kinematics of young stars in the Milky Way disc: First results from SDSS-V
Artikel i vetenskaplig tidskrift, 2025
We present a first large-scale kinematic map of ∼50 000 young OB stars (Teff ≥ 10 000 K), based on BOSS spectroscopy from the Milky Way Mapper OB programme in the ongoing Sloan Digital Sky Survey V (SDSS-V). Using photogeometric distances, line-of-sight velocities, and Gaia DR3 proper motions, we mapped 3D galactocentric velocities across the Galactic plane to ∼ 5 kpc from the Sun, with a focus on radial motions (vR ). Our results reveal mean radial motion with amplitudes of ±30 km/s that are coherent on kiloparsec scales, alternating between inward and outward motions. These v̄ R amplitudes are considerably higher than those observed for older red-giant populations. These kinematic patterns show only a weak correlation with spiral arm over-densities. Age estimates, derived from MIST isochrones, indicate that 85% of the sample is younger than ∼300 Myr and that the youngest stars (≤30 Myr) align well with density enhancements. The age-dependent v̄R in Auriga makes it plausible that younger stars exhibit different velocity variations than older giants. The origin of the radial-velocity features remains uncertain, and it may result from a combination of factors, including spiral-arm dynamics, the Galactic bar, resonant interactions, or phase mixing following a perturbation. The present analysis is based on approximately one-third of the full target sample. The completed survey will enable a more comprehensive investigation of these features and a detailed dynamical interpretation.
Galaxy: kinematics and dynamics
stars: early-type
Galaxy: disk
Galaxy: structure
Författare
Eleonora Zari
Universita degli Studi di Firenze
Jaime Villaseñor
Max-Planck-Gesellschaft
Marina Kounkel
University of North Florida
H. W. Rix
Max-Planck-Gesellschaft
Neige Frankel
Institut canadien d'astrophysique théorique
University of Toronto
A. Tkachenko
KU Leuven
Sergey Khoperskov
Leibniz-Institut Für Astrophysik Potsdam
E. Donghia
University of Wisconsin Madison
A. Roman-Lopes
Universidad de La Serena
Carlos G. Román-Zúñiga
Universidad Nacional Autónoma de México
Guy S. Stringfellow
University of Colorado
Jonathan Tan
Chalmers, Rymd-, geo- och miljövetenskap
University of Virginia
Aida Wofford
Universidad Nacional Autónoma de México
Dmitry Bizyaev
Moscow State University
Apache Point Observatory
John Donor
Texas Christian University
José G. Fernández-Trincado
Universidad Catolica del Norte
Sean Morrison
University of Illinois
Kaike Pan
Apache Point Observatory
S. Sánchez
Universidad Nacional Autónoma de México
Andrew Saydjari
Princeton University
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 703 A303Ämneskategorier (SSIF 2025)
Astronomi, astrofysik och kosmologi
DOI
10.1051/0004-6361/202556444