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

• Published in: Astronomy and astrophysics (Berlin) 2005-04, Vol.434 (1), p.301-308
• Main Authors: DEL PELOSO, E. F, DA SILVA, L, ARANY-PRADO, L. I
• Format: Article
• Language: English
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:20042438

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 less than or equal to [Fe/H] less than or equal to +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 super(+) sub(-) super(5) sub(4) super(.) sub(.) super(8) sub(1) Gyr), and by comparing [Th/Eu] vs. [Fe/H] curves from the model to our stellar abundance ratio data ((8.2 plus or minus 1.9) Gyr), yielding the final, average value (8.3 plus or minus 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.