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The Gaia-ESO Survey : Churning through the Milky Way

Hayden, M. R.; Recio-Blanco, A.; De Laverny, P.; Mikolaitis, S.; Guiglion, G.; Hill, V.; Gilmore, G.; Randich, S.; Bayo, A. and Bensby, T. LU , et al. (2018) In Astronomy and Astrophysics 609.
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... (More)

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.

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published
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keywords
Galaxy: disk, Galaxy: kinematics and dynamics, Galaxy: stellar content, Galaxy: structure
in
Astronomy and Astrophysics
volume
609
publisher
EDP Sciences
external identifiers
  • scopus:85041407949
ISSN
0004-6361
DOI
10.1051/0004-6361/201730412
language
English
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yes
id
629f1774-319d-4d1f-89e1-a9baef465bb1
date added to LUP
2018-02-16 07:57:53
date last changed
2018-11-21 21:38:04
@article{629f1774-319d-4d1f-89e1-a9baef465bb1,
  abstract     = {<p>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] &gt; 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] &gt; 0.1), we find that more than half have small eccentricities (e&lt; 0.2) or are on nearly circular orbits. Slightly more than 20% of the metal-rich stars have perigalacticons R<sub>p</sub>&gt; 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<sup>-1</sup>. 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<sup>-1</sup> 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.</p>},
  articleno    = {A79},
  author       = {Hayden, M. R. and Recio-Blanco, A. and De Laverny, P. and Mikolaitis, S. and Guiglion, G. and Hill, V. and Gilmore, G. and Randich, S. and Bayo, A. and Bensby, T. and Bergemann, M. and Bragaglia, A. and Casey, A. and Costado, M. and Feltzing, S. and Franciosini, E. and Hourihane, A. and Jofre, P. and Koposov, S. and Kordopatis, G. and Lanzafame, A. and Lardo, C. and Lewis, J. and Lind, K. and Magrini, L. and Monaco, L. and Morbidelli, L. and Pancino, E. and Sacco, G. and Stonkute, E. and Worley, C. C. and Zwitter, T.},
  issn         = {0004-6361},
  keyword      = {Galaxy: disk,Galaxy: kinematics and dynamics,Galaxy: stellar content,Galaxy: structure},
  language     = {eng},
  month        = {01},
  publisher    = {EDP Sciences},
  series       = {Astronomy and Astrophysics},
  title        = {The Gaia-ESO Survey : Churning through the Milky Way},
  url          = {http://dx.doi.org/10.1051/0004-6361/201730412},
  volume       = {609},
  year         = {2018},
}