The Flare and Warp of the Young Stellar Disk traced with LAMOST DR5 OB-type stars

Yu, Yang; Wang, Hai-Feng; Cui, Wen-Yuan; Li, Lin-Lin; Liu, Chao; Zhang, Bo; Tian, Hao; Huo, Zhen-Yan; Ju, Jie; Liu, Zhi-Cun; Wen, Fang; Feng, Shuai

doi:10.48550/arxiv.2102.00731

Cited by 2 publications

(3 citation statements)

References 40 publications

(77 reference statements)

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“…For instance, López-Corredoira et al (2002) found a strong flare beginning well inside R 0 based on 2MASS red clump giants. To the contrary, López-Corredoira & Molgó (2014) and Yu et al (2021) found that the flare begins at R 10 kpc by using samples of SDSS-SEGUE F8V-G5V stars and LAM-OST OB stars respectively. In recent studies, the flaring of a disk has been detected not only for our home galaxy but also for the external galaxies (Borlaff 2016;Pinna et al 2019;Kasparova et al 2020), which means that a flared disk could be a common structure in disk galaxies.…”

Section: Discussionmentioning

confidence: 96%

Vertical structure of Galactic disk kinematics from LAMOST K giants

Ding,

Xue,

Yang

et al. 2021

Preprint

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We examine the vertical structure of Galactic disk kinematics over a Galactocentric radial distance range of R = 5-15 kpc and up to 3 kpc away from the Galactic plane, using the K-type giants surveyed by LAMOST. Based on robust measurements of three-dimensional velocity moments, a wobbly disk is detected in a phenomenological sense. An outflow dominates the radial motion of the inner disk, while in the outer disk there exist alternate outward and inward flows. The vertical bulk velocities is a combination of breathing and bending modes. A contraction-like breathing mode with amplitudes increasing with the distance to the plane and an upward bending mode dominate the vertical motion outside R 0 , and there are reversed breathing mode and bending mode at R < R 0 , with amplitudes much smaller than those outside R 0 . The mean azimuthal velocity decreases with the increasing distance to the plane, with gradients shallower for larger R. Stars in the south disk are rotating faster than stars in the north. The velocity ellipsoid orientation differs between different R: in the range of 5 < R < 9 kpc, the gradient of the tilt angle with respect to arctan(Z/R) decreases from ∼ 0.83 for the inner disk to ∼ 0.52 for the outer disk; within 9 < R < 15 kpc, the tilt of velocity ellipsoid deviates from vertical antisymmetry. A clear flaring signature is found for both north and south disks based on the observed vertical structures of velocity ellipsoid.

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Section: Discussionmentioning

confidence: 96%

Vertical structure of Galactic disk kinematics from LAMOST K giants

Ding,

Xue,

Yang

et al. 2021

Preprint

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“…Warps in stellar disc of galaxies were first discovered by van der Kruit & Searle (1981). Large surveys of galaxies have since then shown that stellar warps are present in 40 to 75% of galaxies, depending on the nature of the sample (Reshetnikov & Combes 1998;Ann & Park 2006).…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, disc heating and warping may happen simultaneously. Indeed, the outskirts of the MW's disc seem to be both flaring (e.g., Amôres et al 2017;López-Corredoira et al 2018;Thomas et al 2018) and warping (e.g., Chen et al 2019;Yu et al 2021). Khachaturyants et al (2021) suggested that settled warp stars may contribute to the flaring of the youngest stellar populations observed at large galactocentric radii in the MW.…”

Section: Introductionmentioning

confidence: 99%

No memory of past warps in the vertical density structure of galaxies

Cruz¹,

Martig²,

Minchev

2021

Preprint

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Warps are observed in a large fraction of disc galaxies, and can be due to a large number of different processes. Some of these processes might also cause vertical heating and flaring. Using a sample of galaxies simulated in their cosmological context, we study the connection between warping and disc heating. We analyse the vertical stellar density structure within warped stellar discs, and monitor the evolution of the scale-heights of the mono-age populations and the geometrical thin and thick disc during the warp's lifetime. We also compare the overall thickness and the vertical velocity dispersion in the disc before and after the warp. We find that for warps made of pre-existing stellar particles shifted off-plane, the scale-heights do not change within the disc's warped region: discs tilt rigidly. For warps made of off-plane new stellar material (either born in-situ or accreted), the warped region of the disc is not well described by a double sech 2 density profile. Yet, once the warp is gone, the thin and thick disc structure is recovered, with their scale-heights following the same trends as in the region that was never warped. Finally, we find that the overall thickness and vertical velocity dispersion do not increase during a warp, regardless of the warp's origin. This holds even for warps triggered by interactions with satellites, which cause disc heating but before the warp forms. Our findings suggest that the vertical structure of galaxies does not hold any memory of past warps.

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The Flare and Warp of the Young Stellar Disk traced with LAMOST DR5 OB-type stars

Cited by 2 publications

References 40 publications

Vertical structure of Galactic disk kinematics from LAMOST K giants

Vertical structure of Galactic disk kinematics from LAMOST K giants

No memory of past warps in the vertical density structure of galaxies

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