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Evidence for Population-dependent Vertical Motions and the Long-lived Nonsteady Lopsided Milky Way Warp

Li, X; Wang, HF; Luo, YP; López-Corredoira, M; Ting, YS; Chrobáková, Ž; (2023) Evidence for Population-dependent Vertical Motions and the Long-lived Nonsteady Lopsided Milky Way Warp. The Astrophysical Journal , 943 (2) , Article 88. 10.3847/1538-4357/acab5b. Green open access

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Abstract

We present a Galactic disk vertical velocity analysis using OB type stars (OB stars), red clump (RC) stars, and main-sequence turnoff (MSTO) stars with different average age populations crossmatched with LAMOST DR5 and Gaia DR3. We show that the vertical velocities of the three populations clearly vary with the Galactocentric distance (R) and the younger stellar population has a stronger increasing trend in general. The bending and breathing modes indicated by the vertical motions are dependent on the populations and vary with spatial locations. These vertical motions may be due to the Galactic warp, or minor mergers, or nonequilibrium of the disk. Assuming the warp is the dominant component, we find that the amplitude of the warp (γ, Z ω ) of OB stars (younger population) is larger than that of RC stars (medium population) and the latter is also larger than that for MSTO stars (older population), which is in agreement with other independent analyses of stellar density distribution, and supports that the warp is a long-lived, nonsteady structure and is time evolving. This conclusion is robust whether the line of nodes ϕ w is fixed or is a free parameter (with ϕ w being around 3°−8.°5 as the best fit). Furthermore, we find that the warp is lopsided with asymmetries along the azimuthal angle (ϕ).

Type: Article
Title: Evidence for Population-dependent Vertical Motions and the Long-lived Nonsteady Lopsided Milky Way Warp
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/1538-4357/acab5b
Publisher version: https://doi.org/10.3847/1538-4357/acab5b
Language: English
Additional information: Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10202952
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