Abundances of Cu and Zn in metal-poor stars: Clues for Galaxy evolution^*

¹ Odessa Astronomical Observatory, and Isaac Newton Institute of Chile, Odessa Branch, Shevchenko Park, Odessa 65014, Ukraine e-mail: tamar@deneb.odessa.ua; val@deneb.odessa.ua
² Observatoire de Bordeaux, CNRS UNR 5804, BP 89, 33270 Floirac, France e-mail: soubiran@observ.u-bordeaux.fr
³ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85741 Garching bei München, Germany e-mail: claudia@mpa-garching.mpg.de
⁴ Istituto Nazionale di Astrofisica (INAF) – Osservatorio Astronomico di Torino, via Osservatorio 20, 10025 Pino Torinese (To), Italy
⁵ Department of Physics, University of Perugia, Italy e-mail: busso@pg.infn.it

Corresponding author: T. V. Mishenina, tamar@deneb.odessa.ua

Received: 7 May 2002
Accepted: 20 September 2002

Abstract

We present new observations of copper and zinc abundances in 90 metal-poor stars, belonging to the metallicity range . The present study is based on high resolution spectroscopic measurements collected at the Haute Provence Observatoire (, ). The trend of Cu and Zn abundances as a function of the metallicity [Fe/H] is discussed and compared to that of other heavy elements beyond iron. We also estimate spatial velocities and galactic orbital parameters for our target stars in order to disentangle the population of disk stars from that of halo stars using kinematic criteria. In the absence of a firm a priori knowledge of the nucleosynthesis mechanisms controlling Cu and Zn production, and of the relative stellar sites, we derive constraints on these last from the trend of the observed ratios [Cu/Fe] and [Zn/Fe] throughout the history of the Galaxy, as well as from a few well established properties of basic nucleosynthesis processes in stars. We thus confirm that the production of Cu and Zn requires a number of different sources (neutron captures in massive stars, s-processing in low and intermediate mass stars, explosive nucleosynthesis in various supernova types). We also attempt a ranking of the relative roles played by different production mechanisms, and verify these hints through a simple estimate of the galactic enrichment in Cu and Zn. In agreement with suggestions presented earlier, we find evidence that type Ia Supernovae must play a relevant role, especially for the production of Cu.