Detalles de publicación
PP 019078
Mapping the Galactic disk with the LAMOST and Gaia Red clump sample. Part III: A new velocity substructure and time stamps of the Galactic disk asymmetry in the disk between 12−15 kpc
(1) South−Western Institute for Astronomy Research, Yunnan University, Kunming, 650500, P. R. China; (2) Department of Astronomy, China West Normal University, Nanchong 637009, China; (3) LSST, 950 North Cherry Avenue, Tucson, AZ 85719, USA; 4) IAC; (5) ULL
We investigate the three-dimensional asymmetrical kinematics and present time stamps of the Milky Way disk between Galactocentric distances of R=12 and 15
kpc, using red clump stars selected from the LAMOST Galactic survey, also with proper motion measurements provided by the Gaia DR2. We discover velocity substructure above the Galactic plane corresponding to a density dip found recently ("south-middle opposite" density structure[R ∼ 12-15 kpc, Z ∼ 1.5 kpc] discovered in Wang et al. (2018b,2018c) in the radial and azimuthal velocity. For the vertical velocity, we detect clear vertical bulk motions or bending mode motions, which has no clear north-south asymmetry corresponding to the in-plane asymmetrical features. In the subsample of stars with different ages, we find that there is little temporal evolution of the in-plane asymmetry from 0−14 Gyr, which means the structure is sensitive to the perturbations in almost cosmic time possibly. We propose that the possible scenario of this asymmetric velocity structure is caused by the mechanisms generated in-plane, rather than vertical perturbations.
kpc, using red clump stars selected from the LAMOST Galactic survey, also with proper motion measurements provided by the Gaia DR2. We discover velocity substructure above the Galactic plane corresponding to a density dip found recently ("south-middle opposite" density structure[R ∼ 12-15 kpc, Z ∼ 1.5 kpc] discovered in Wang et al. (2018b,2018c) in the radial and azimuthal velocity. For the vertical velocity, we detect clear vertical bulk motions or bending mode motions, which has no clear north-south asymmetry corresponding to the in-plane asymmetrical features. In the subsample of stars with different ages, we find that there is little temporal evolution of the in-plane asymmetry from 0−14 Gyr, which means the structure is sensitive to the perturbations in almost cosmic time possibly. We propose that the possible scenario of this asymmetric velocity structure is caused by the mechanisms generated in-plane, rather than vertical perturbations.