The Gaia-ESO Survey: Separating disk chemical substructures with cluster models

Abstract

(Abridged) Recent spectroscopic surveys have begun to explore the Galactic disk system outside the solar neighborhood on the basis of large data samples. In this way, they provide valuable information for testing spatial and temporal variations of disk structure kinematics and chemical evolution. We used a Gaussian mixture model algorithm, as a rigurous mathematical approach, to separate in the [Mg/Fe] vs. [Fe/H] plane a clean disk star subsample from the Gaia-ESO survey internal data release 2. We find that the sample is separated into five groups associated with major Galactic components; the metal-rich end of the halo, the thick disk, and three subgroups for the thin disk sequence. This is confirmed with a sample of red clump stars from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. The two metal-intermediate and metal-rich groups of the thin disk decomposition ([Fe/H]>-0.25 dex) highlight a change in the slope at solar metallicity. This holds true at different radial regions. The distribution of Galactocentric radial distances of the metal-poor part of the thin disk ([Fe/H]<-0.25 dex) is shifted to larger distances than those of the more metal-rich parts. Moreover, the metal-poor part of the thin disk presents indications of a scale height intermediate between those of the thick and the rest of the thin disk, and it displays higher azimuthal velocities than the latter. These stars might have formed and evolved in parallel and/or dissociated from the inside-out formation taking place in the internal thin disk. Their enhancement levels might be due to their origin from gas pre-enriched by outflows from the thick disk or the inner halo. The smooth trends of their properties (their spatial distribution with respect to the plane, in particular) with [Fe/H] and [Mg/Fe] suggested by the data indicates a quiet dynamical evolution, with no relevant merger events.

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Cited by in corpus (11)

• PLATO as it is: a legacy mission for Galactic archaeology
• APOGEE DR16: a multi-zone chemical evolution model for the Galactic disc based on MCMC methods
• Recent advances in the determination of some Galactic constants in the Milky Way
• The GALAH survey: properties of the Galactic disk(s) in the solar neighbourhood
• The Gaia-ESO Survey: low-alpha element stars in the Galactic Bulge
• Most "young" $\alpha$-rich stars have high masses but are actually old
• Median Statistics Estimate of the Galactic Rotational Velocity
• Correlations between age, kinematics, and chemistry as seen by the RAVE survey
• Spectroscopy of Dwarf Stars Around the North Celestial Pole
• Insights into the Formation and Evolution History of the Galactic Disk System
• High-resolution spectroscopic study of dwarf stars in the northern sky: Na to Zn abundances in two fields with radii of 20 degrees