The Gaia-ESO Survey: Churning through the Milky Way

Abstract

We attempt to determine the relative fraction of stars that have undergone significant radial migration by studying the orbital properties of metal-rich ([Fe/H]$>0.1$) stars within 2 kpc of the Sun using a sample of more than 3,000 stars selected from iDR4 of the Gaia-ESO Survey. We investigate the kinematic properties, such as velocity dispersion and orbital parameters, of stellar populations near the sun as a function of [Mg/Fe] and [Fe/H], which could show evidence of a major merger in the past history of the Milky Way. This was done using the stellar parameters from the Gaia-ESO Survey along with proper motions from PPMXL to determine distances, kinematics, and orbital properties for these stars to analyze the chemodynamic properties of stellar populations near the Sun. Analyzing the kinematics of the most metal-rich stars ([Fe/H]$>0.1$), we find that more than half have small eccentricities ($e<0.2$) or are on nearly circular orbits. Slightly more than 20\% of the metal-rich stars have perigalacticons $R_p>7$ kpc. We find that the highest [Mg/Fe], metal-poor populations have lower vertical and radial velocity dispersions compared to lower [Mg/Fe] populations of similar metallicity by $\sim 10$ km s${}^{-1}$. The median eccentricity increases linearly with [Mg/Fe] across all metallicities, while the perigalacticon decreases with increasing [Mg/Fe] for all metallicities. Finally, the most [Mg/Fe]-rich stars are found to have significant asymmetric drift and rotate more than 40 km s${}^{-1}$ slower than stars with lower [Mg/Fe] ratios. While our results cannot constrain how far stars have migrated, we propose that migration processes are likely to have played an important role in the evolution of the Milky Way, with metal-rich stars migrating from the inner disk toward to solar neighborhood and past mergers potentially driving enhanced migration of older stellar populations in the disk.

7 pages, 7 Figures, accepted A&A

References in corpus (7)

• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• galpy: A Python Library for Galactic Dynamics
• The Radial Velocity Experiment (RAVE): first data release
• The Gaia-ESO Survey: the Galactic Thick to Thin Disc transition
• Automated derivation of stellar atmospheric parameters and chemical abundances: the MATISSE algorithm
• The effect of radial migration on galactic disks
• The Radical Consequences of Realistic Satellite Orbits for the Heating and Implied Merger Histories of Galactic Disks

Cited by in corpus (18)

• The Gaia-ESO Public Spectroscopic Survey: Implementation, data products, open cluster survey, science, and legacy
• The GALAH survey: tracing the Galactic disk with Open Clusters
• The AMBRE project: The thick thin disk and thin thick disk of the Milky Way
• Stellar migrations and metal flows -- Chemical evolution of the thin disc of a simulated Milky Way analogous galaxy
• Revisiting long-standing puzzles of the Milky Way: the Sun and its vicinity as typical outer disk chemical evolution
• Chronology of our Galaxy from Gaia Colour-Magnitude Diagram-fitting (ChronoGal). I. The formation and evolution of the thin disk from the Gaia Catalogue of Nearby Stars
• Kinematic properties of white dwarfs. Galactic orbital parameters and age-velocity dispersion relation
• Migration and Mixing in the Galactic Disc from Encounters between Sagittarius and the Milky Way
• Timing the Milky Way bar formation and the accompanying radial migration episode
• The Gaia-ESO Survey: Oxygen abundance in the Galactic thin and thick disks
• The Gaia-ESO Survey: Old super-metal-rich visitors from the inner Galaxy
• Tracing birth properties of stars with abundance clustering
• Insights into the Formation and Evolution History of the Galactic Disk System
• The chemical enrichment of the Milky Way disk evaluated using conditional abundances
• The Gaia spectroscopic catalogue of exoplanets and host stars
• On the genesis of spiral galaxies -- Classical and pseudo bulges as extremities of a continuous sequence
• CN and CO Features: Key Indicators of Red Giant Evolutionary Phase in Moderate-Resolution X-Shooter Spectra
• Relatively young thick disks in star-forming late-type galaxies