Deciphering the evolution of the Milky Way discs: <i>Gaia</i> APOGEE <i>Kepler</i> giant stars and the Besançon Galaxy Model

Context. Thanks to ongoing efforts compute accurate stellar ages, we are able characterise stars in different regions of the Milky Way. The Gaia and Kepler space-missions, along with ground-based spectroscopic surveys such as APOGEE, provide a unique way study chemo-kinematics relations function age through Galactic populations new constraints evolution models. Aims. We investigate properties double sequences Way discs visible [ α /Fe] versus [Fe/H] diagram, which usually associated chemical thin thick at solar circle. In framework formation evolution, discuss complex relationships between age, metallicity, /Fe], radial, azimuthal, vertical components space velocities. Methods. measured seismic from APOGEE survey satellite, respectively. addition, astrometry satellite is available for majority sample. separate /Fe]−[Fe/H] diagram into three populations: disc, high- metal-poor metal-rich disc each these age-chemo-kinematics parameter space. Because model-dependent nature ages inferred asteroseismology, because they depend on quality input information, compare results obtained data releases (DR14 DR16). also use determinations two recent works literature. Besançon synthesis model highlight selection biases mechanisms (such mergers secular evolution) not included model. Results. exhibits flat age–metallicity relation while increases age. confirm no correlation radial velocities [Fe/H], population. Considering both samples, V φ decreases disc. show that this difference due sample selection. Although distribution very close 7 14 Gyr, its kinematics seems follow This feature, predicted by hypotheses Galaxy Model, suggests origin history Finally, there maximum dispersion velocity, σ Z , around 8 Gyr. comparisons Model simulations suggest more chemo-dynamical scheme explain most likely including migration effects.