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The Gaia-ESO Survey: metallicity and kinematic trends in the Milky Way bulge

Rojas-Arriagada, A.; Recio-Blanco, A.; Hill, V.; de Laverny, P.; Schultheis, M.; Babusiaux, C.; Zoccali, M.; Minniti, D.; Gonzalez, O. A. and Feltzing, Sofia LU , et al. (2014) In Astronomy & Astrophysics 569.
Abstract
Aims. Observational studies of the Milky Way bulge are providing increasing evidence of its complex chemo-dynamical patterns and morphology. Our intent is to use the iDR1 Gaia-ESO Survey (GES) data set to provide new constraints on the metallicity and kinematic trends of the Galactic bulge, exploring the viability of the currently proposed formation scenarios. Methods. We analyzed the stellar parameters and radial velocities of similar to 1200 stars in five bulge fields wich are located in the region -10 degrees < / < 7 degrees and -10 degrees < b < -4 degrees. We use VISTA Variables in the Via Lactea (VVV) photometry to verify the internal consistency of the atmospheric parameters recommended by the consortium. As a... (More)
Aims. Observational studies of the Milky Way bulge are providing increasing evidence of its complex chemo-dynamical patterns and morphology. Our intent is to use the iDR1 Gaia-ESO Survey (GES) data set to provide new constraints on the metallicity and kinematic trends of the Galactic bulge, exploring the viability of the currently proposed formation scenarios. Methods. We analyzed the stellar parameters and radial velocities of similar to 1200 stars in five bulge fields wich are located in the region -10 degrees < / < 7 degrees and -10 degrees < b < -4 degrees. We use VISTA Variables in the Via Lactea (VVV) photometry to verify the internal consistency of the atmospheric parameters recommended by the consortium. As a by-product, we obtained reddening values using a semi-empirical Tdf -color calibration. We constructed the metallicity distribution functions and combined them with photometric and radial velocity data to analyze the properties of the stellar populations in the observed fields. Results. From a Gaussian decomposition of the metallicity distribution functions, we unveil a clear bimodality in all fields, with the relative size of components depending of the specific position on the sky. In agreement with some previous studies, we find a mild gradient along the minor axis (-0.05 dex/deg between b = -6 degrees and b = -10 degrees) that arises from the varying proportion of metal-rich and metal-poor components. The number of metal-rich stars fades in favor of the metal-poor stars with increasing b. The K-magnitude distribution of the metal-rich population splits into two peaks for two of the analyzed fields that intersects the near and far branches of the X-shaped bulge structure. In addition, two lateral fields at (l,b) = (7, -9) and (l, b) = (-10, 8) present contrasting characteristics. In the former, the metallicity distribution is dominated by metal-rich stars, while in the latter it presents a mix of a metal-poor population and and a metal-intermediate one, of nearly equal sizes. Finally, we find systematic differences in the velocity dispersion between the metal-rich and the metal-poor components of each field. Conclusions. The iDR I bulge data show chemo-dynamical distributions that are consistent with varying proportions of stars belonging to (i) a metal-rich boxy/peanut X-shaped component, with bar-like kinematics; and (ii) a metal-poor more extended rotating structure with a higher velocity dispersion that dominates far from the Galactic plane. These first GES data already allow studying the detailed spatial dependence of the Galactic bulge populations, thanks to the analysis of individual fields with relatively high statistics. (Less)
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keywords
Galaxy: formation, Galaxy: abundances, Galaxy: bulge, Galaxy: stellar, content, stars: abundances
in
Astronomy & Astrophysics
volume
569
publisher
EDP Sciences
external identifiers
  • wos:000343092100093
  • scopus:84907546769
ISSN
0004-6361
DOI
10.1051/0004-6361/201424121
language
English
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yes
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ffefbd8a-bf65-41d6-8996-397706a0997a (old id 4783817)
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2014-11-21 10:43:40
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@article{ffefbd8a-bf65-41d6-8996-397706a0997a,
  abstract     = {Aims. Observational studies of the Milky Way bulge are providing increasing evidence of its complex chemo-dynamical patterns and morphology. Our intent is to use the iDR1 Gaia-ESO Survey (GES) data set to provide new constraints on the metallicity and kinematic trends of the Galactic bulge, exploring the viability of the currently proposed formation scenarios. Methods. We analyzed the stellar parameters and radial velocities of similar to 1200 stars in five bulge fields wich are located in the region -10 degrees &lt; / &lt; 7 degrees and -10 degrees &lt; b &lt; -4 degrees. We use VISTA Variables in the Via Lactea (VVV) photometry to verify the internal consistency of the atmospheric parameters recommended by the consortium. As a by-product, we obtained reddening values using a semi-empirical Tdf -color calibration. We constructed the metallicity distribution functions and combined them with photometric and radial velocity data to analyze the properties of the stellar populations in the observed fields. Results. From a Gaussian decomposition of the metallicity distribution functions, we unveil a clear bimodality in all fields, with the relative size of components depending of the specific position on the sky. In agreement with some previous studies, we find a mild gradient along the minor axis (-0.05 dex/deg between b = -6 degrees and b = -10 degrees) that arises from the varying proportion of metal-rich and metal-poor components. The number of metal-rich stars fades in favor of the metal-poor stars with increasing b. The K-magnitude distribution of the metal-rich population splits into two peaks for two of the analyzed fields that intersects the near and far branches of the X-shaped bulge structure. In addition, two lateral fields at (l,b) = (7, -9) and (l, b) = (-10, 8) present contrasting characteristics. In the former, the metallicity distribution is dominated by metal-rich stars, while in the latter it presents a mix of a metal-poor population and and a metal-intermediate one, of nearly equal sizes. Finally, we find systematic differences in the velocity dispersion between the metal-rich and the metal-poor components of each field. Conclusions. The iDR I bulge data show chemo-dynamical distributions that are consistent with varying proportions of stars belonging to (i) a metal-rich boxy/peanut X-shaped component, with bar-like kinematics; and (ii) a metal-poor more extended rotating structure with a higher velocity dispersion that dominates far from the Galactic plane. These first GES data already allow studying the detailed spatial dependence of the Galactic bulge populations, thanks to the analysis of individual fields with relatively high statistics.},
  articleno    = {A103},
  author       = {Rojas-Arriagada, A. and Recio-Blanco, A. and Hill, V. and de Laverny, P. and Schultheis, M. and Babusiaux, C. and Zoccali, M. and Minniti, D. and Gonzalez, O. A. and Feltzing, Sofia and Gilmore, G. and Randich, S. and Vallenari, A. and Alfaro, E. J. and Bensby, Thomas and Bragaglia, A. and Flaccomio, E. and Lanzafame, A. C. and Pancino, E. and Smiljanic, R. and Bergemann, M. and Costado, M. T. and Damiani, F. and Hourihane, A. and Jofre, P. and Lardo, C. and Magrini, L. and Maiorca, E. and Morbidelli, L. and Sbordone, L. and Worley, C. C. and Zaggia, S. and Wyse, R.},
  issn         = {0004-6361},
  keyword      = {Galaxy: formation,Galaxy: abundances,Galaxy: bulge,Galaxy: stellar,content,stars: abundances},
  language     = {eng},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {The Gaia-ESO Survey: metallicity and kinematic trends in the Milky Way bulge},
  url          = {http://dx.doi.org/10.1051/0004-6361/201424121},
  volume       = {569},
  year         = {2014},
}