Letter to the Editor

Dynamical evidence of the age-metallicity relation in the Milky Way disk

¹ Observatório do Valongo, Universidade Federal do Rio de Janeiro, Ladeira do Pedro Antônio 43, 20080-090 Rio de Janeiro RJ, Brazil e-mail: helio@ov.ufrj.br
² Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, R. do Matão 1226, 05508-900 São Paulo SP, Brazil

Received: 4 April 2006
Accepted: 1 May 2006

Abstract

Aims.We studied the relationship between the average stellar abundance of several elements and the orbital evolution of stars in the neighbourhood of the Sun.

Methods.We used both observational data for 325 late-type dwarfs in a volume-complete sample and simulations of the orbital diffusion. Metallicities, ages, and initial position and velocities for the simulated stars are sampled from empirical distributions of these quantities in the Milky Way.

Results.We found that that there is a relationship between the average stellar abundance of Fe, Na, Si, Ca, Ni, and Ba and the mean orbital radius of stars currently passing through the solar neighbourhood. The greater the difference between the mean orbital radius and the solar Galactocentric distance, the more deficient the star is, on average, in these chemical species.

Conclusions.The stars that take a longer time to come from their birthplaces to arrive in the present solar neighbourhood are more likely to be more metal-poor than those that were born here. This result is a direct, independent indication that a tightly defined Galactic age-metallicity relation exists.