High-Precision Ages and Abundances: Unlocking the Milky Way's History

Abstract: Chemical clocks, such as abundance ratios between s-process and alpha-elements, are powerful tools for estimating stellar ages in spectroscopic surveys. I present a detailed spectroscopic analysis of 68 Kepler red giants, combining high-precise abundances with high-precise asteroseismic ages (precision <10%) to calibrate chemical clock-age relations. I also show how high-precision in chemical abundances and stellar ages is fundamental to obtain relations precise enough to use this promising tool. These calibrations enable accurate “chemical ages” for ~270,000 stars in the APOGEE and Gaia-ESO surveys, revealing age trends across stellar populations. Key results include distinguishing low- and high-alpha sequences, the age-metallicity relation, disc flaring, and a population of old metal-rich stars. Additionally, I investigate the [C/N] ratio, a chemical clock sensitive to mixing during the RGB phase, using Kepler-APOGEE red giants. Comparing observed [C/N]-age trends with stellar models, I apply mixing corrections to derive birth-[C/N] abundances and validate Galactic evolution models.