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The Gaia-ESO Survey: New constraints on the Galactic disc velocity dispersion and its chemical dependencies

Guiglion, G.; Recio-Blanco, A.; de Laverny, P.; Kordopatis, G.; Hill, V.; Mikolaitis, S.; Minchev, I.; Chiappini, C.; Wyse, R. F. G. and Gilmore, G., et al. (2015) In Astronomy & Astrophysics 583.
Abstract
Context. Understanding the history and the evolution of the Milky Way is one of the main goals of modern astrophysics. In particular, the formation of the Galactic disc is a key problem of Galactic archaeology. Aims. We study the velocity dispersion behaviour of Galactic disc stars as a function of the [Mg/Fe] ratio, which for small metallicity bins can be used as a proxy of relative age. This key relation is essential to constrain the formation mechanisms of the disc stellar populations as well as the cooling and settling processes. Methods. We used the recommended parameters and chemical abundances of 7800 FGK Milky Way field stars from the second internal data release of the Gaia-ESO spectroscopic Survey. These stars were observed with... (More)
Context. Understanding the history and the evolution of the Milky Way is one of the main goals of modern astrophysics. In particular, the formation of the Galactic disc is a key problem of Galactic archaeology. Aims. We study the velocity dispersion behaviour of Galactic disc stars as a function of the [Mg/Fe] ratio, which for small metallicity bins can be used as a proxy of relative age. This key relation is essential to constrain the formation mechanisms of the disc stellar populations as well as the cooling and settling processes. Methods. We used the recommended parameters and chemical abundances of 7800 FGK Milky Way field stars from the second internal data release of the Gaia-ESO spectroscopic Survey. These stars were observed with the GIRAFFE spectrograph (HR10 and HR21 setups), and cover a large spatial volume in the intervals 6 < R < 10 kpc and vertical bar Z vertical bar < 2 kpc. Based on a chemical criterion, we separated the thin- from the thick-disc sequence in the [Mg/Fe] vs. [Fe/H] plane. Results. From analysing the Galactocentric velocity of the stars for the thin disc, we find a weak positive correlation between 170 and [Fe/H] that is due to a slowly rotating [Fe/H]-poor tail. For the thick disc stars, a strong correlation with [Fe/H] and [Mg/Fe] is established. In addition, we have detected an inversion of the velocity dispersion trends with [Mg/Fe] for thick-disc stars with [Fe/H] < -0.10 dex and [Mg/Fe] > +0.20 dex for the radial component. First, the velocity dispersion increases with [Mg/Fe] at all [Fe/H] ratios for the thin-disc stars, and then it decreases for the thick-disc population at the highest [Mg/Fe] abundances Similar trends are observed for several bins of [Mg/Fe] within the errors for the azimuthal velocity dispersion, while a continuous increase with [Mg/Fe] is observed for the vertical velocity dispersion. The velocity dispersion decrease agrees with previous measurements of the RAVE survey, although it is observed here for a greater metallicity interval and a larger spatial volume. Conclusions. Thanks to the Gaia-ESO Survey data, we confirm the existence of [Mg/Fe]-rich thick-disc stars with cool kinematics in the generally turbulent context of the primitive Galactic disc. This is discussed in the framework of the different disc formation and evolution scenarios. (Less)
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keywords
Galaxy: abundances, Galaxy: disk, Galaxy: kinematics and dynamics, Galaxy: stellar content, stars: abundances
in
Astronomy & Astrophysics
volume
583
publisher
EDP Sciences
external identifiers
  • wos:000365072200030
  • scopus:84946594981
ISSN
0004-6361
DOI
10.1051/0004-6361/201525883
language
English
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yes
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1b0ed2a7-ef6c-4cd3-b4e7-01b9f3893e58 (old id 8539586)
date added to LUP
2016-01-20 12:54:16
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2017-09-17 06:02:13
@article{1b0ed2a7-ef6c-4cd3-b4e7-01b9f3893e58,
  abstract     = {Context. Understanding the history and the evolution of the Milky Way is one of the main goals of modern astrophysics. In particular, the formation of the Galactic disc is a key problem of Galactic archaeology. Aims. We study the velocity dispersion behaviour of Galactic disc stars as a function of the [Mg/Fe] ratio, which for small metallicity bins can be used as a proxy of relative age. This key relation is essential to constrain the formation mechanisms of the disc stellar populations as well as the cooling and settling processes. Methods. We used the recommended parameters and chemical abundances of 7800 FGK Milky Way field stars from the second internal data release of the Gaia-ESO spectroscopic Survey. These stars were observed with the GIRAFFE spectrograph (HR10 and HR21 setups), and cover a large spatial volume in the intervals 6 &lt; R &lt; 10 kpc and vertical bar Z vertical bar &lt; 2 kpc. Based on a chemical criterion, we separated the thin- from the thick-disc sequence in the [Mg/Fe] vs. [Fe/H] plane. Results. From analysing the Galactocentric velocity of the stars for the thin disc, we find a weak positive correlation between 170 and [Fe/H] that is due to a slowly rotating [Fe/H]-poor tail. For the thick disc stars, a strong correlation with [Fe/H] and [Mg/Fe] is established. In addition, we have detected an inversion of the velocity dispersion trends with [Mg/Fe] for thick-disc stars with [Fe/H] &lt; -0.10 dex and [Mg/Fe] &gt; +0.20 dex for the radial component. First, the velocity dispersion increases with [Mg/Fe] at all [Fe/H] ratios for the thin-disc stars, and then it decreases for the thick-disc population at the highest [Mg/Fe] abundances Similar trends are observed for several bins of [Mg/Fe] within the errors for the azimuthal velocity dispersion, while a continuous increase with [Mg/Fe] is observed for the vertical velocity dispersion. The velocity dispersion decrease agrees with previous measurements of the RAVE survey, although it is observed here for a greater metallicity interval and a larger spatial volume. Conclusions. Thanks to the Gaia-ESO Survey data, we confirm the existence of [Mg/Fe]-rich thick-disc stars with cool kinematics in the generally turbulent context of the primitive Galactic disc. This is discussed in the framework of the different disc formation and evolution scenarios.},
  articleno    = {A91},
  author       = {Guiglion, G. and Recio-Blanco, A. and de Laverny, P. and Kordopatis, G. and Hill, V. and Mikolaitis, S. and Minchev, I. and Chiappini, C. and Wyse, R. F. G. and Gilmore, G. and Randich, S. and Feltzing, Sofia and Bensby, Thomas and Flaccomio, E. and Koposov, S. E. and Pancino, E. and Bayo, A. and Costado, M. T. and Franciosini, E. and Hourihane, A. and Jofre, P. and Lardo, C. and Lewis, J. and Lind, K. and Magrini, L. and Morbidelli, L. and Sacco, G. G. and Ruchti, Gregory and Worley, C. C. and Zaggia, S.},
  issn         = {0004-6361},
  keyword      = {Galaxy: abundances,Galaxy: disk,Galaxy: kinematics and dynamics,Galaxy: stellar content,stars: abundances},
  language     = {eng},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {The Gaia-ESO Survey: New constraints on the Galactic disc velocity dispersion and its chemical dependencies},
  url          = {http://dx.doi.org/10.1051/0004-6361/201525883},
  volume       = {583},
  year         = {2015},
}