The Gaia-ESO Survey: Churning through the Milky Way

Research output: Contribution to journalArticle

Abstract

Context. There have been conflicting results with respect to the extent that radial migration has played in the evolution of the Galaxy. Additionally, observations of the solar neighborhood have shown evidence of a merger in the past history of the Milky Way that drives enhanced radial migration. Aims. 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. We also aim to 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. Methods. We used a sample of more than 3000 stars selected from the fourth internal data release of the Gaia-ESO Survey. We used 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. Results. 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 Rp> 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 ~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. Conclusions. 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.

Details

Authors
  • M. R. Hayden
  • A. Recio-Blanco
  • P. De Laverny
  • S. Mikolaitis
  • G. Guiglion
  • V. Hill
  • G. Gilmore
  • S. Randich
  • A. Bayo
  • M. Bergemann
  • A. Bragaglia
  • A. Casey
  • M. Costado
  • E. Franciosini
  • A. Hourihane
  • P. Jofre
  • S. Koposov
  • G. Kordopatis
  • A. Lanzafame
  • C. Lardo
  • J. Lewis
  • K. Lind
  • L. Magrini
  • L. Monaco
  • L. Morbidelli
  • E. Pancino
  • G. Sacco
  • E. Stonkute
  • C. C. Worley
  • T. Zwitter
Organisations
External organisations
  • Université Nice Sophia Antipolis
  • Vilnius University
  • University of Cambridge
  • INAF - Osservatorio Astrofisico di Arcetri
  • Max Planck Institute for Astronomy
  • INAF Osservatorio Astronomico di Bologna
  • CSIC Instituto de Astrofísica de Andalucía (IAA)
  • Leibniz Institute for Astrophysics Potsdam (AIP)
  • University of Catania
  • Osservatorio Astrofisico di Catania
  • Liverpool John Moores University
  • Uppsala University
  • Andrés Bello National University
  • University of Ljubljana
  • Côte d'Azur Observatory
  • University of Valparaíso
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology

Keywords

  • Galaxy: disk, Galaxy: kinematics and dynamics, Galaxy: stellar content, Galaxy: structure
Original languageEnglish
Article numberA79
JournalAstronomy and Astrophysics
Volume609
Publication statusPublished - 2018 Jan 1
Publication categoryResearch
Peer-reviewedYes

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