The age of the Galactic thin disk from Th/Eu nucleocosmochronology - II. Chronological analysis

The purpose of this work is to resume investigation of Galactic thin disk dating using nucleocosmochronology with Th/Eu stellar abundance ratios, a theme absent from the literature since 1990. [Th/Eu] abundance ratios for a sample of 20 disk dwarfs/subgiants of F5 to G8 spectral type with -0.8 < [Fe/H] < +0.3, determined in the first paper of this series, were adopted for this analysis. We developed a Galactic chemical evolution model that includes the effect of refuse, which are composed of stellar remnants (white dwarfs, neutron stars and black holes) and low-mass stellar formation residues (terrestrial planets, comets, etc.), contributing to a better fit to observational constraints. Two Galactic disk ages were estimated, by comparing literature data on Th/Eu production and solar abundance ratios to the model (8.7 +5.8 -4.1 Gyr), and by comparing [Th/Eu] vs. [Fe/H] curves from the model to our stellar abundance ratio data ((8.2 ± 1.9) Gyr), yielding the final, average value (8.3 ± 1.8) Gyr. This is the first Galactic disk age determined via Th/Eu nudeocosniochronology, and corroborates the most recent white dwarf ages determined via cooling sequence calculations, which indicate a low age (<10 Gyr) for the disk.