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

Li, Xiang; Wang, Hai-Feng; Luo, Yangping; López-Corredoira, Martín; Ting, Yuan-Sen; Chrobáková, Ž.

doi:10.3847/1538-4357/acab5b

Cited by 5 publications

(1 citation statement)

References 94 publications

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“…Meanwhile, the older population is weaker than the younger population for the break, which might also not be consistent with the influence caused by the secular evolution of the bar. Moreover, the difference between OB stars and main-sequence turnoff stars for the intriguing break around 11-12 kpc has also been confirmed in our recent work in Li et al (2023), which is used to discuss warp properties. So it is reasonable to ask whether or not the break is caused by the warp dynamics in consideration of the V Z break and younger populations are stronger than old populations (Wang et al 2020b;Chrobáková et al 2022), the origin of the warp could possibly be gas direct infall onto the disk and Sgr interactions (López-Corredoira 2019b and reference therein).…”

Section: More Comparisons and The Bar Contributionsupporting

confidence: 70%

Kinematic-chemical Analysis and Time Tagging for the Diagonal Ridge Structure of the Galactic Outer Disk with LAMOST Red-giant Branch Stars

Yang

Wang

Zhi-Quan

et al. 2023

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We investigate the kinematic-chemical distribution of red-giant branch stars from the LAMOST survey crossed matched with Gaia DR2 proper motions, and present time tagging for the well-known ridge structures (diagonal distributions for V R in the R, V ϕ plane) in the range of Galactocentric distance R = 8 to 15 kpc. We detect six ridge structures, including five ridges apparent in the radial velocity distribution and three ridges apparent in the vertical velocity, the sensitive time of which to the perturbations are from young population (0–3 Gyr) to old population (9–14 Gyr). Based on an analysis of the evolution of angular momentum distribution, we find that four ridges are relatively stationary, while another is evolving with time, which is confirmed by the difference analysis at different populations and supporting that there might be two kinds of dynamical origins. Furthermore, ridge features are also vividly present in the chemical properties ([Fe/H], [α/Fe]). The comparison between the north and south hemispheres of the Galaxy does show some differences and the ridge features are asymmetrical. Moreover, we find that diagonal ridge structures may affect the shape of the rotation curve, which is manifested as fluctuations and undulations on top of a smooth profile. Finally we speculate that the bar dynamics should be not enough to explain all ridge properties including the break feature in the V Z –L Z plane.

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Section: More Comparisons and The Bar Contributionsupporting

confidence: 70%

Kinematic-chemical Analysis and Time Tagging for the Diagonal Ridge Structure of the Galactic Outer Disk with LAMOST Red-giant Branch Stars

Yang

Wang

Zhi-Quan

et al. 2023

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Detection of the Keplerian decline in the Milky Way rotation curve

Jiao,

Hammer,

Wang

et al. 2023

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Our position inside the Galactic disc has previously prevented us from establishing an accurate rotation curve (RC). The advent of Gaia and its third data release (Gaia DR3) made it possible to specify the RC up to twice the optical radius. We aim to establish a new RC of the Galaxy from the Gaia DR3 by drastically reducing systematic uncertainties. Our goal is to provide a new estimate of the mass of the Galaxy. We compared different estimates, established a robust assessment of the systematic uncertainties, and addressed differences in methodologies, particularly regarding distance estimates. We find a sharply decreasing RC for the Milky Way; the decrease in velocity between 19.5 and 26.5 kpc is approximately 30 km s−1. We identify, for the first time, a Keplerian decline of the RC, starting at ∼19 kpc and ending at ∼26.5 kpc from the Galaxy centre, while a flat RC is rejected with a significance of 3σ. The total mass is revised downwards to 2.06−0.13+0.24 × 1011 M⊙, which is in agreement with the absence of a significant mass increase at radii larger than 19 kpc. We evaluated the upper limit on the total mass by considering the upper values of velocity measurements, which leads to a strict, unsurpassable limit of 5.4 × 1011 M⊙.

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Warp and flare of the old Galactic disc as traced by the red clump stars

Uppal,

Ganesh,

Schultheis

2023

Monthly Notices of the Royal Astronomical Society

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Our study aims to investigate the outer disc structure of the Milky Way galaxy using the red clump (RC) stars. We analysed the distribution of the largest sample of RC stars to date, homogeneously covering the entire Galactic plane in the range of 40○ ≤ ℓ ≤ 340○ and −10○ ≤ b ≤ +10○. This sample allows us to model the RC star distribution in the Galactic disc to better constrain the properties of the flare and warp of the Galaxy. Our results show that the scale length of the old stellar disc weakly depends on azimuth, with an average value of 1.95 ± 0.26 kpc. On the other hand, a significant disc flaring is detected, where the scale height of the disc increases from 0.38 kpc in the solar neighbourhood to ∼2.2 kpc at R ≈15 kpc. The flare exhibits a slight asymmetry, with ∼1 kpc more scale height below the Galactic plane as compared to the Northern flare. We also confirm the warping of the outer disc, which can be modelled with Zw = (0.0057 ± 0.0050) [R − (7358 ± 368)(pc)]1.40 ± 0.09sin (φ − ( − 2○.03 ± 0○.18)). Our analysis reveals a noticeable north-south asymmetry in the warp, with a greater amplitude observed in the southern direction compared to the northern. Comparing our findings with younger tracers from the literature, we observe an age dependency of both the flare and warp. An increase in flare strength with age suggests the secular evolution of the disc as the preferred mechanism for forming the flare. The increase of the maximum warp amplitude with age indicates that the warp dynamics could be the possible cause of the variation in the warp properties with age.

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

Cited by 5 publications

References 94 publications

Kinematic-chemical Analysis and Time Tagging for the Diagonal Ridge Structure of the Galactic Outer Disk with LAMOST Red-giant Branch Stars

Kinematic-chemical Analysis and Time Tagging for the Diagonal Ridge Structure of the Galactic Outer Disk with LAMOST Red-giant Branch Stars

Detection of the Keplerian decline in the Milky Way rotation curve

Warp and flare of the old Galactic disc as traced by the red clump stars

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