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

Abstract

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 refuses, 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 nucleocosmochronology, and corroborates the most recent white dwarf ages determined via cooling sequence calculations, which indicate a low age (<~ 10 Gyr) for the disk.

arXiv comment9 pages, 7 Postscript figures, accepted for publication in Astronomy & Astrophysics, final version

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• Constraints on the Proper Motion of the Andromeda Galaxy Based on the Survival of Its Satellite M33
• The age of the Galactic thin disk from Th/Eu nucleocosmochronology III. Extended sample
• Thorium in solar twins: implications for habitability in rocky planets
• The age of the Galactic thin disk from Th/Eu nucleocosmochronology I. Determination of [Th/Eu] abundance ratios
• Enrichment of the Galactic disc with neutron-capture elements: Gd, Dy, and Th
• Astrophysics in 2005