The GALAH Survey: Chemodynamics of the Solar Neighbourhood

Abstract

We present the chemodynamic structure of the solar neighbourhood using 62 814 stars within a 500 pc sphere of the Sun observed by GALAH and with astrometric parameters from Gaia DR2. We measure the velocity dispersion for all three components (vertical, radial, and tangential) and find that it varies smoothly with [Fe/H] and [$\alpha$/Fe] for each component. The vertical component is especially clean, with ${\sigma }_{v_z}$ increasing from a low of $8$ km s${}^{-1}$ at solar-[$\alpha$/Fe] and [Fe/H] to a high of more than 50 km s${}^{-1}$ for more metal-poor and [$\alpha$/Fe] enhanced populations. We find no evidence of a large decrease in the velocity dispersion of the higher-[$\alpha$/Fe] populations as claimed in analysis prior to Gaia DR2, although the trend of increasing velocity dispersion with [$\alpha$/Fe] for the same metallicity does significantly flatten at high-[$\alpha$/Fe]. The eccentricity distribution for local stars varies most strongly as a function of [$\alpha$/Fe], where stars with [$\alpha$/Fe]$<0.1$ dex having generally circular orbits ($e<0.15$), while the median eccentricity increases rapidly for more [$\alpha$/Fe]-enhanced stellar populations up to $e\sim 0.35$. These [$\alpha$/Fe]-enhanced populations have guiding radii consistent with origins in the inner Galaxy. Of the stars with metallicities much higher than the local ISM ([Fe/H]>0.1 dex), we find that more than 70\% have $e<0.2$ and are likely observed in the solar neighbourhood through churning/migration rather than blurring effects, as the epicyclic motion for these stars is not large enough to reach the radii at which they were likely born based on their metallicity.

arXiv comment11 pages, 8 figures, submitted to MNRAS

References in corpus (74)

• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• Local Kinematics and the Local Standard of Rest
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• galpy: A Python Library for Galactic Dynamics
• SEGUE: A Spectroscopic Survey of 240,000 stars with g=14-20
• The New Galaxy: Signatures of its Formation
• GAIA: Composition, Formation and Evolution of the Galaxy
• Radial Mixing in Galactic Discs
• The Radial Velocity Experiment (RAVE): first data release
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• The GALAH Survey: Scientific Motivation
• Chemical evolution with radial mixing
• The KMOS^3D Survey: design, first results, and the evolution of galaxy kinematics from 0.7<z<2.7
• LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) The survey science plan
• The age structure of stellar populations in the solar vicinity. Clues of a two-phase formation history of the Milky Way disk
• A dynamically young and perturbed Milky Way disk
• Estimating distances from parallaxes
• Present-day cosmic abundances. A comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models
• Chemodynamical evolution of the Milky Way disk I: The solar vicinity
• Spectroscopy Made Easy: Evolution
• The Cannon: A data-driven approach to stellar label determination
• A New Mechanism for Radial Migration in Galactic Disks: Spiral-Bar Resonance Overlap
• The GALAH Survey: Second Data Release
• Secular Evolution in Disk Galaxies
• Galaxia: a code to generate a synthetic survey of the Milky Way
• Kinematics and history of the solar neighbourhood revisited
• The Milky Way's Stellar Disk
• The Gaia-ESO Survey: the Galactic Thick to Thin Disc transition
• The Distribution of the Elements in the Galactic Disk III. A Reconsideration of Cepheids from l = 30 to 250 Degrees
• The GALAH survey and Gaia DR2: dissecting the stellar disc's phase space by age, action, chemistry and location
• The Milky Way has no in-situ halo other than the heated thick disc. Composition of the stellar halo and age-dating the last significant merger with Gaia DR2 and APOGEE
• Dynamical heating across the Milky Way disc using APOGEE and $Gaia$
• Formation and Evolution of the Disk System of the Milky Way: [alpha/Fe] Ratios and Kinematics of the SEGUE G-Dwarf Sample
• Chemodynamics of the Milky Way. I. The first year of APOGEE data
• HII Region Metallicity Distribution in the Milky Way Disk
• The Gaia-ESO Survey: radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk
• Estimating stellar birth radii and the time evolution of the Milky Way's ISM metallicity gradient
• Radial Migration Does Little for Galactic Disc Thickening
• Chemical Cartography with APOGEE: Large-scale Mean Metallicity Maps of the Milky Way
• Red giants observed by CoRoT and APOGEE: The evolution of the Milky Way's radial metallicity gradient
• The TESS-HERMES survey Data Release 1: high-resolution spectroscopy of the TESS southern continuous viewing zone
• Kinematic modelling of the Milky Way using the RAVE and GCS stellar surveys
• The Distribution of the Elements in the Galactic Disk II. Azimuthal and Radial Variation in Abundances from Cepheids
• The GALAH survey: An abundance, age, and kinematic inventory of the solar neighbourhood made with TGAS
• The Galactic Disc in Action Space as seen by Gaia DR2
• The effect of radial migration on galactic disks
• Radial Migration in Galactic Thick Discs
• The vertical motions of mono-abundance sub-populations in the Milky Way disk
• Transient spiral structure and the disc velocity substructure in Gaia DR2
• The AMBRE project: The thick thin disk and thin thick disk of the Milky Way
• Slicing and dicing the Milky Way disk in SDSS
• A new stellar chemo-kinematic relation reveals the merger history of the Milky Way disc
• The Rich Are Different: Evidence from the RAVE Survey for Stellar Radial Migration
• Galactic abundance gradients from Cepheids: alpha and heavy elements in the outer disk
• The age-velocity dispersion relation of the Galactic discs from LAMOST-Gaia data
• Project overview and update on WEAVE: the next generation wide-field spectroscopy facility for the William Herschel Telescope
• Fast estimation of orbital parameters in Milky-Way-like potentials
• The GALAH survey: The data reduction pipeline
• Chemo-orbital evidence from SDSS/SEGUE G-type dwarf stars for a mixed origin of the Milky Way's thick disk
• Evidence of a thick disk rotation-metallicity correlation
• The Gaia-ESO Survey: New constraints on the Galactic disc velocity dispersion and its chemical dependencies
• The K2-HERMES Survey. I. Planet Candidate Properties from K2 Campaigns 1-3
• Observational Evidence from SDSS for a Merger Origin of the Milky Way's Thick Disk
• Constraining churning and blurring in the Milky Way using large spectroscopic surveys -- an exploratory study
• The GALAH Survey: Accurate Radial Velocities and Library of Observed Stellar Template Spectra
• The GALAH Survey: Stellar streams and how stellar velocity distributions vary with Galactic longitude, hemisphere and metallicity
• Constraints on Radial Migration in Spiral Galaxies - II. Angular momentum distribution and preferential migration
• The Gaia-ESO Survey: Churning through the Milky Way
• The imprint of radial migration on the vertical structure of galaxy disks
• The velocity ellipsoid in the Galactic disc using Gaia DR1
• Cardinal kinematics: I. Rotation fields of the APOGEE Survey
• Dynamical Evolution of Disk Galaxies

Cited by in corpus (46)

• The GALAH+ Survey: Third Data Release
• VINTERGATAN I: The origins of chemically, kinematically and structurally distinct discs in a simulated Milky Way-mass galaxy
• The GALAH survey: tracing the Galactic disk with Open Clusters
• Stars with Photometrically Young Gaia Luminosities Around the Solar System (SPYGLASS) I: Mapping Young Stellar Structures and their Star Formation Histories
• Fundamental relations for the velocity dispersion of stars in the Milky Way
• VINTERGATAN II: the history of the Milky Way told by its mergers
• Stellar migrations and metal flows -- Chemical evolution of the thin disc of a simulated Milky Way analogous galaxy
• Bimodality of [α/Fe]-[Fe/H] distributions is a natural outcome of dissipative collapse and disc growth in Milky Way-type galaxies
• The s Process and Beyond
• VINTERGATAN III: how to reset the metallicity of the Milky Way
• A precise asteroseismic age and metallicity for HD 139614: a pre-main-sequence star with a protoplanetary disc in Upper-Centaurus Lupus
• The Gaia-ESO survey: 3D NLTE abundances in the open cluster NGC 2420 suggest atomic diffusion and turbulent mixing at the origin of chemical abundance variations
• The GALAH survey: A census of lithium-rich giant stars
• Evidence for Galactic disc RR~Lyrae stars in the Solar neighbourhood
• Constraining churning and blurring in the Milky Way using large spectroscopic surveys -- an exploratory study
• Chemo-kinematics of the Milky Way spiral arms and bar resonances: connection to ridges and moving groups in the Solar vicinity
• Mapping the Galactic disk with the LAMOST and $Gaia$ Red clump sample: V: On the origin of the "young" [$\alpha$/Fe]-enhanced stars
• The stellar velocity distribution function in the Milky Way galaxy
• The GALAH Survey: Chemical Clocks
• From giant clumps to clouds -- II. The emergence of thick disc kinematics from the conditions of star formation in high redshift gas rich galaxies
• Kinematic properties of white dwarfs. Galactic orbital parameters and age-velocity dispersion relation
• Icarus: a Flat and Fast Prograde Stellar Stream in the Milky Way disk
• Gyrochronological dating of the stellar moving group Group X
• Timing the Milky Way bar formation and the accompanying radial migration episode
• The AMBRE Project: Spectrum normalisation influence on Mg abundances in the metal-rich Galactic disc
• SPYGLASS. II. The Multi-Generational and Multi-Origin Star Formation History of Cepheus Far North
• The AMBRE Project: Solar neighbourhood chemodynamical constraints on Galactic disc evolution
• Universal properties of the high- and low-α disk: small intrinsic abundance scatter and migrating stars
• Age-metallicity dependent stellar kinematics of the Milky Way disc from LAMOST and Gaia
• A Spectroscopic Analysis of the California-Kepler Survey Sample: II. Correlations of Stellar Metallicities with Planetary Architectures
• Can ultralight dark matter explain the age-velocity dispersion relation of the Milky Way disc: A revised and improved treatment
• Asteroseismology of $\delta$ Scuti stars: emulating model grids using a neural network
• A Unified Exploration of the Chronology of the Galaxy
• Insights into the Formation and Evolution History of the Galactic Disk System
• Double Red Giant Branch and Red Clump features of Galactic disc stellar populations with Gaia GSPspec
• The chemical enrichment of the Milky Way disk evaluated using conditional abundances
• A binary with a $\delta$~Scuti star and an oscillating red giant: orbit and asteroseismology of KIC9773821
• The Gaia spectroscopic catalogue of exoplanets and host stars
• The tilt of the velocity ellipsoid of different Galactic disk populations
• A Spectroscopic Analysis of a Sample of K2 Planet-Host Stars: Stellar Parameters, Metallicities and Planetary Radii
• Towards a fully consistent Milky Way disk model V. The disk model for 4 $-$ 14 kpc
• New stellar age estimates using SPInS based on Gaia DR3 photometry and LAMOST DR8 abundances
• CN and CO Features: Key Indicators of Red Giant Evolutionary Phase in Moderate-Resolution X-Shooter Spectra
• Spectral Evidence of Solar Neighborhood Analogs in CALIFA Galaxies
• The SAMI Survey: Evidence for dynamical coupling of ionised gas and young stellar populations
• New families in our Solar neighborhood: applying Gaussian Mixture models for objective classification of structures in the Milky Way and in simulations