The Gaia -ESO Survey: Metallicity and kinematic trends in the Milky Way bulge
No hay miniatura disponible
Archivos
Fecha
2014-09
Profesor/a Guía
Facultad/escuela
Idioma
en
Título de la revista
ISSN de la revista
Título del volumen
Editor
EDP Sciences
Nombre de Curso
Licencia CC
Atribution 4.0 International (CC BY 4.0)
Licencia CC
https://creativecommons.org/licenses/by/4.0/deed.es
Resumen
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 ∼1200 stars in five bulge fields wich are located in the region −10◦ < l < 7
◦
and −10◦ < b < −4
◦
. 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 Teff-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
◦
and b = −10◦
) 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 iDR1 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.
Notas
Indexación: Scopus.
Palabras clave
Galaxy: Formation, Galaxy: Abundances, Galaxy: Bulge, Galaxy: stellar content, Stars: Abundances
Citación
Astronomy and Astrophysics. Volume 569. 1 September 2014. Article number A103
DOI
DOI: 10.1051/0004-6361/201424121