Insights on the Milky Way bulge formation from the correlations between kinematics and metallicity

By C. Babusiaux, A. Gómez, V. Hill, F. Royer, M. Zoccali, Frédéric Arenou, R. Fux, A. Lecureur, M. Schultheis, B. Barbuy and 2 more. 2010

152 citations recorded by the source corpus.

Context. Two main scenarios for the formation of the Galactic bulge are invoked, the first one through gravitational collapse or hierarchical merging of subclumps, the second through secular evolution of the Galactic disc. Aims. We aim to constrain the formation of the Galactic bulge through studies of the correlation between kinematics and metallicities in Baade's Window (l = 1°, b = -4°) and two other fields along the bulge minor axis (l = 0°, b = -6° and b = -12°). Methods. We combine the radial velocity and the [Fe/H] measurements obtained with FLAMES/GIRAFFE at the VLT with a spectral resolution of R = 20 000, plus for the Baade's Window field the OGLE-II proper motions, and compare these with published N-body simulations of the Galactic bulge. Results. We confirm the presence of two distinct populations in Baade's Window found in Hill et al. (2010, A&A, submitted): the metal-rich population presents bar-like kinematics while the metal-poor population shows kinematics corresponding to an old spheroid or a thick disc. In this context the metallicity gradient along the bulge minor axis observed by Zoccali et al. (2008, A&A, 486, 177), visible also in the kinematics, can be related to a varying mix of these two populations as one moves away from the Galactic plane, alleviating the apparent contradiction between the kinematic evidence of a bar and the existence of a metallicity gradient. Conclusions. We show evidence that the two main scenarios for the bulge formation co-exist within the Milky Way bulge.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/a1901ad6f3fab6af6145318506258e45027d4e81

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Citations in the corpus

The metallicity distribution of bulge clump giants in Baade’s window (2011, methodology): “As explained in Babusiaux et al. (2010), the kinematical characteristics of the richest population suggest that it is under the influence of a bar.”
THE LUMINOSITY PROFILE AND STRUCTURAL PARAMETERS OF THE ANDROMEDA GALAXY (2011, background): “Similar conclusions have been drawn for the Milky Way; Babusiaux et al. (2010) report the presence of two distinct populations in Baade’s Window with a metal-rich population with barlike kinematics and a metal-poor population with kinematics indicative of an old population.”
TWO RED CLUMPS AND THE X-SHAPED MILKY WAY BULGE (2010, background): “Recently, Zoccali et al. (2010), Hill et al. (2010, unpublished) and Babusiaux et al. (2010) claimed that the bulge metallicity gradient of Zoccali et al. (2008) is an artifact, due to a changing ratio of two populations of bulge stars with different metallicities and kinematics.”
Mapping the three-dimensional density of the galactic bulge with VVV red clump stars (2013, background): “Figure 18 shows a projection of the density along the intermediate axis i.e. a side on view of the Milky Way Bulge.”
Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS II. The complete high resolution extinction map and implications for Galactic bulge studies (2012, background): “…al. 2007); iii) in addition to the population associated with the bar, there are hints of a second chemically and kinematically distinct component (Babusiaux et al. 2010; Hill et al. 2011; Gonzalez et al. 2011b; Bensby et al. 2011); and iv) the GB is dominated by old stars (Zoccali et al. 2003;…”
Nucleosynthesis in Stars and the Chemical Enrichment of Galaxies (2013, background): “Recent observational data suggest two populations in the Galactic bulge: a metal-rich bar and a metalpoor classical bulge (Babusiaux et al. 2010, Hill et al. 2011, Uttenthaler et al. 2012; but see Ness & Freeman 2012).”
Stellar populations in the Milky Way bulge region: towards solving the Galactic bulge and bar shapes using 2MASS data (2011, methodology): “…studied the MDF and radial velocity distribution from the RGB, Gonzalez et al. (2011) completed the data with the abundances of alpha abundances, Babusiaux et al (2010) studied the correlation between metallicity and kinematics and Hill et al (2011) computed the MDF from the red clump giants…”
Alpha element abundances and gradients in the Milky Way bulge from FLAMES-GIRAFFE spectra of 650 K giants (2011, background): “The most metal-rich part of the population, that shows a downturn in [α/Fe] has formed on a timescale long enough for SNIa to start contributing significantly with iron peak elements and shows kinematics corresponding to a disk/bar component according to Babusiaux et al. (2010).”
Chemical tagging with APOGEE: Discovery of a large population of N-rich stars in the inner Galaxy (2016, background): “…halo (e.g., Babusiaux et al. 2010; Ness et al. 2013a,b; Rojas-Arriagada et al. 2014) or perhaps even a classical c© 2015 RAS spheroidal bulge (e.g., Babusiaux et al. 2010; Hill et al. 2011), although the existence of the latter has been called into question by model fits to stellar counts in the…”
REDDENING AND EXTINCTION TOWARD THE GALACTIC BULGE FROM OGLE-III: THE INNER MILKY WAY'S RV ∼ 2.5 EXTINCTION CURVE (2012, background): “There is also evidence that the metal-poor stars are distributed as a classical bulge (Babusiaux et al. 2010; De Propris et al. 2011; Uttenthaler et al. 2012), whereas the data on metal-rich M-giants are consistent with entirely cold kinematics (Kunder et al. 2012).”
ARGOS - III. Stellar populations in the Galactic bulge of the Milky Way (2012, methodology): “For stars in this abundance range, Babusiaux et al. (2010) measur a vertex deviation in Baade’s window oflv = −43◦ ± 5◦ .”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “They could represent an old bulge formed through early mergers or a thick disk component participating in the instability together with the inner stellar halo (e.g., Babusiaux et al. 2010, Di Matteo et al. 2014).”