Torus Models of the Outer Disc of the Milky Way using LAMOST Survey Data

Abstract

With a sample of 48,161 K giant stars selected from the LAMOST DR 2 catalogue, we construct torus models in a large volume extending, for the first time, from the solar vicinity to a Galactocentric distance of $\sim 20$ kpc, reaching the outskirts of the Galactic disc. We show that the kinematics of the K giant stars match conventional models, e.g. as created by Binney in 2012, in the Solar vicinity. However such two-disc models fail if they are extended to the outer regions, even if an additional disc component is utilised. If we loosen constraints in the Sun's vicinity, we find that an effective thick disc model could explain the anti-centre of the MW. The LAMOST data imply that the sizes of the Galactic discs are much larger, and that the outer disc is much thicker, than previously thought, or alternatively that the outer structure is not a conventional disc at all. However, the velocity dispersion ${\sigma }_{0z}$ of the kinematically thick disc in the best-fitting model is about 80 km s${}^{-1}$ and has a scale parameter $R_{\sigma }$ for an exponential distribution function of $\sim 19$ kpc. Such a height ${\sigma }_{0z}$ is strongly rejected by current measurements in the solar neighbourhood, and thus a model beyond quasi-thermal, two or three thin or thick discs is required.

arXiv comment11 pages, 7 figures and 3 tables, Accepted for publication in MNRAS

References in corpus (45)

• The Sloan Digital Sky Survey: Technical Summary
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• Local Kinematics and the Local Standard of Rest
• The Geneva-Copenhagen survey of the Solar neighbourhood: Ages, metallicities, and kinematic properties of 14,000 F and G dwarfs
• galpy: A Python Library for Galactic Dynamics
• The Radial Velocity Experiment (RAVE): first data release
• The GALAH Survey: Scientific Motivation
• Mass models of the Milky Way
• The Milky Way's Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from Kinematics of ~2400 SDSS Blue Horizontal Branch Stars
• LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) The survey science plan
• A direct dynamical measurement of the Milky Way's disk surface density profile, disk scale length, and dark matter profile at 4 kpc < R < 9 kpc
• Mass models of the Milky Way
• Galactoseismology: Discovery of Vertical Waves in the Galactic Disk
• The wobbly Galaxy: kinematics north and south with RAVE red clump giants
• The Bulge Radial Velocity Assay (BRAVA): II. Complete Sample and Data Release
• Rings and Radial Waves in the Disk of the Milky Way
• The stellar population structure of the Galactic disk
• On the Shoulders of Giants: Properties of the Stellar Halo and the Milky Way Mass Distribution
• The Milky Way's rotation curve out to 100 kpc and its constraint on the Galactic mass distribution
• Constraining the Galaxy's dark halo with RAVE stars
• Made-to-measure N-body systems
• Made-to-Measure models of the Galactic Box/Peanut bulge: stellar and total mass in the bulge region
• APOGEE: The Apache Point Observatory Galactic Evolution Experiment
• ARGOS II: The Galactic Bulge Survey
• Estimating distances from parallaxes. III. Distances of two million stars in the Gaia DR1 catalogue
• Substructure in bulk velocities of Milky Way disk stars
• The Bulge Radial Velocity Assay (BRAVA): I. Techniques and a Rotation Curve
• Label Transfer from APOGEE to LAMOST: Precise Stellar Parameters for 450,000 LAMOST Giants
• The radial profile and flattening of the Milky Way's stellar halo to $80$kpc from the SEGUE K-giant Survey
• A review of action estimation methods for galactic dynamics
• A radial age gradient in the geometrically thick disk of the Milky Way
• The K giant stars from the LAMOST survey data I: identification, metallicity, and distance
• Disassembling the Galaxy with angle-action coordinates
• More dynamical models of our Galaxy
• Galactic kinematics and dynamics from RAVE stars
• The distribution function of the Galaxy's dark halo
• A New Model for the Milky Way Bar
• Torus mapper: a code for dynamical models of galaxies
• Made-to-measure galaxy models - III Modelling with Milky Way observations
• Discovery of a Dynamical Cold Point in the Heart of the Sagittarius dSph Galaxy with Observations from the APOGEE Project
• A fast algorithm for estimating actions in triaxial potentials
• Estimation of distances to stars with stellar parameters from LAMOST
• A Schwarzschild model of the Galactic bar with initial density from N-body simulations
• The site conditions of the Guo Shou Jing Telescope
• The local spiral arm in the LAMOST-Gaia common stars?

Cited by in corpus (10)

• Gaia Early Data Release 3: The Galactic anticentre
• Mapping the Milky Way with LAMOST III: Complicated spatial structure in the outer disc
• Orbital tori for non-axisymmetric galaxies
• The fall of the Northern Unicorn: Tangential motions in the Galactic Anti-centre with SDSS and Gaia
• Disk stars in the Milky Way detected beyond 25 kpc from its center
• Classifying globular clusters and applying them to estimate the mass of the Milky Way
• The Data Processing of the LAMOST Medium-Resolution Spectral Survey of Galactic Nebulae (LAMOST MRS-N Pipeline)
• Orbit properties of massive prolate galaxies in the Illustris simulation
• Rediscovering the Galactic outer disk with LAMOST data
• Dynamical Models of the Milky Way in Action Space with LAMOST DR8 and GAIA EDR3