Solving the mixing puzzle in giant stars using the Galactic Stellar Population Synthesis Model

The current (and future) large Galactic surveys are revolutionising our knowledge of Galactic and stellar physics, providing kinematics, chemical and global properties for a very large number of stars across the Milky Way. Despite a rich observational background, few spectroscopic studies have dealt with the measurement of the carbon isotopic ratio in giant stars. However, it is a key element in understanding the mixing mechanisms that occur in the interiors of giant stars. We have determined the abundances of CNO, particularly focusing on the carbon isotopic ratio, using the high-resolution FIbre-fed Echelle Spectrograph on the Nordic Optical Telescope for 71 giant field stars. Furthermore, asteroseismology data from the Kepler satellite is available for all stars, providing information on their stellar mass, age, and evolutionary states. Additionally, astrometry data from the Gaia mission is accessible for the majority of the sample. We compare these new determinations with stellar evolution models that incorporate the effects of transport processes. To exploit the complete potential of our extensive catalogue and considering both the Milky Way’s evolution and the impact of stellar evolution, we built mock catalogues using the Besançon Galaxy model in which stellar evolution models taking into account the effects of thermohaline instability are included. Recent results published in Lagarde et al (2024) are presented through this poster. I show the comparison between observations and mock catalogs, discussing the impact of extra mixing concerning stellar metallicity, age, and mass, as well as considering different stellar populations.