Tracing the Milky Way: Calibrating chemical ages with high-precision Kepler data

TL;DR

This study calibrates chemical clocks using high-precision spectroscopic and asteroseismic data from Kepler red giants, enabling improved stellar age estimations and insights into Galactic evolution.

Contribution

It introduces new chemical age relations based on high-resolution abundances, enhancing age precision and applicability across stellar populations.

Findings

[Ce/Mg] and [Zr/Ti] ratios tightly correlate with stellar ages

Chemical clocks differentiate between low- and high-alpha stellar populations

Revealed Galactic disc features like flaring and old metal-rich stars

Abstract

Chemical clocks offer a powerful tool for estimating stellar ages from spectroscopic surveys. We present a new detailed spectroscopic analysis of 68 Kepler red giant stars to provide a suite of high-precision abundances along with asteroseismic ages with better than 10 percent precision from individual mode frequencies. We obtained several chemical clocks as ratios between s-process elements (Y, Zr, Ba, La, Ce) and alpha-elements (Mg, Ca, Si, Al, Ti). Our data show that [Ce/Mg] and [Zr/Ti] display a remarkably tight correlation with stellar ages, with abundance dispersions of 0.08 and 0.01 dex respectively and below 3 Gyr in ages, across the entire Galactic chronochemical history. While improving the precision floor of spectroscopic surveys is critical for broadening the scope and applicability of chemical clocks, the intrinsic accuracy of our relations -- enabled by high-resolution chemical abundances and stellar ages in our sample -- allows us to draw meaningful conclusions about age trends across stellar populations. By applying our relations to the APOGEE and Gaia-ESO surveys, we are able to differentiate the low- and high-alpha sequences in age, recover the age-metallicity relation, observe the disc flaring of the Milky Way, and identify a population of old metal-rich stars.