The tilt of the velocity ellipsoid of different Galactic disk populations

Abstract

The tilt of the velocity ellipsoid is a helpful tracer of the gravitational potential of the Milky Way. In this paper, we use nearly 140,000 RC stars selected from the LAMOST and Gaia to make a detailed analysis of the tilt of the velocity ellipsoid for various populations, as defined by the stellar ages and chemical information, within 4.5 $\le$ $R$ $\le$ 15.0 kpc and $|Z|$ $\le$ 3.0 kpc. The tilt angles of the velocity ellipsoids of the RC sample stars are accurately described as $\alpha$ = ${\alpha }_0$ $\arctan$ ($Z$/$R$) with ${\alpha }_0$ = (0.68 $\pm$ 0.05). This indicates the alignment of velocity ellipsoids is between cylindrical and spherical, implying that any deviation from the spherical alignment of the velocity ellipsoids may be caused by the gravitational potential of the baryonic disk. The results of various populations suggest that the ${\alpha }_0$ displays an age and population dependence, with the thin and thick disks respectively values ${\alpha }_0$ = (0.72 $\pm$ 0.08) and ${\alpha }_0$ = (0.64 $\pm$ 0.07), and the ${\alpha }_0$ displays a decreasing trend with age (and [$\alpha$/Fe]) increases, meaning that the velocity ellipsoids of the kinematically relaxed stars are mainly dominated by the gravitational potential of the baryonic disk. We determine the ${\alpha }_0-R$ for various populations, finding that the ${\alpha }_0$ displays oscillations with $R$ for all the different populations. The oscillations in ${\alpha }_0$ appear in both kinematically hot and cold populations, indicating that resonances with the Galactic bar are the most likely origin for these oscillations.

10 pages, 8 figures, 3 tables, accepted for publication in ApJ

References in corpus (15)

• The Radial Velocity Experiment (RAVE): first data release
• Outer structure of the Galactic warp and flare: explaining the Canis Major over-density
• Gaia Data Release 3: Analysis of RVS spectra using the General Stellar Parametriser from spectroscopy
• The Gaia-ESO Survey: the Galactic Thick to Thin Disc transition
• Rings and Radial Waves in the Disk of the Milky Way
• On the Formation of Galactic Thick Disks
• Young [$\alpha$/Fe]-enhanced stars discovered by CoRoT and APOGEE: What is their origin?
• LAMOST Spectroscopic Survey of the Galactic Anti-centre (LSS-GAC): target selection and the first release of value-added catalogues
• LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC): the second release of value-added catalogues
• Determination of the Local Standard of Rest using the LSS-GAC DR1
• Gaia Data Release 3: Chemical cartography of the Milky Way
• The Rotation Curve, Mass Distribution and Dark Matter Content of the Milky Way from Classical Cepheids
• Mapping the Galactic disk with the LAMOST and Gaia Red clump sample: I: precise distances, masses, ages and 3D velocities of $\sim$ 140000 red clump stars
• Gaia Data Release 3: A Golden Sample of Astrophysical Parameters
• Mapping the Galactic disk with the LAMOST and $Gaia$ Red clump sample: V: On the origin of the "young" [$\alpha$/Fe]-enhanced stars

Cited by in corpus (1)

• Interstellar Meteors from Tidal Disruption of Rocky Planets on Eccentric Orbits Around M Dwarfs