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TwitterA&A 480, 379-395 (2008)
DOI: 10.1051/0004-6361:20064854
Chemical abundances in LMC stellar populations
I. The inner disk sample
L. Pompéia1, 2, V. Hill3, M. Spite3, A. Cole4, 5, F. Primas6, M. Romaniello6, L. Pasquini6, M.-R. Cioni7, and T. Smecker Hane81 IP&D, Universidade do Vale do Paraíba, Av. Shishima Hifumi, 2911, São, José dos Campos, 12244-000 SP, Brazil
2 Instituto Astronômico e Geofísico (USP), Rua do Matão 1226, Cidade Universitária, 05508-900 São Paulo, Brazil
e-mail: pompeia@univap.br
3 Observatoire de Paris-Meudon, GEPI and CNRS UMR 8111, 92195 Meudon Cedex, France
e-mail: [Vanessa.Hill;Monique.Spite]@obspm.fr
4 School of Mathematics and Physics, University of Tasmania, Private Bag 37, Hobart, TAS 7001, Australia
5 Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, The Netherlands
e-mail: cole@astro.rug.nl
6 European Southern Observatory, Karl Schwarschild Str. 2, 85748 Garching b. München, Germany
e-mail: [fprimas;mromanie;lpasquin]@eso.org
7 Edinburg SUPA, School of Physics, University of Edinburgh, IfA, Blackford Hill, Edinburgh EH9 3HJ, UK
e-mail: mrc@roe.ac.uk
8 Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697-4575, USA
e-mail: smecker@carina.ps.uci.edu
(Received 13 January 2006 / Accepted 13 November 2007)
Abstract
Aims.We have used FLAMES (the Fibre Large Array Multi Element
Spectrograph) at the VLT-UT2 telescope to obtain spectra of a
large sample of red giant stars from the inner disk of the LMC, ~2 kpc
from the center of the galaxy. We investigate the chemical abundances of
key elements to understand the star formation and evolution of the
LMC disk: heavy and light [s-process/Fe] and [
/Fe] give
constraints on the time scales of formation of the stellar population.
Cu, Na, Sc, and the iron-peak elements are also studied aiming to better understand
the build up of the elements of this population and the origin of these elements.
We aim to provide a more complete picture of the LMC's evolution by compiling a
large sample of field star abundances.
Methods.LTE abundances were derived using line
spectrum synthesis or equivalent width analysis. We used OSMARCS model atmospheres
and an updated line list.
Results.We find that the alpha-elements Ca, Si, and Ti show lower [X/Fe] ratios
than Galactic stars at the same [Fe/H], with most [Ca/Fe] being
subsolar. The [O/Fe] and [Mg/Fe] ratios are slightly deficient,
with Mg showing some overlap with the Galactic distribution, while Sc
and Na follow the underabundant behavior of Ca, with subsolar
distributions. For the light s-process elements Y and Zr, we find
underabundant values compared to their Galactic counterparts. The [La/Fe] ratios
are slightly overabundant relative to the galactic pattern showing
low scatter, while the [Ba/Fe] are enhanced, with a slight increasing trend
for metallicities [Fe/H] > -1 dex. The [heavy-s/light-s]
ratios are high, showing a slow, increasing trend with
metallicity. We were surprised to find an offset for three of the
iron-peak elements. We found an offset for the
[iron-peak/Fe] ratios of Ni, Cr, and Co, with an underabundant pattern
and subsolar values, while Vanadium ratios track
the solar value. Copper shows very low abundances in our sample
for all metallicities, compatible with those of the Galaxy only
for the most metal-poor stars. The overall chemical distributions
of this LMC sample indicates a slower star formation history relative to
that of the solar neighborhood, with a higher contribution from type Ia
supernovae relative to type II supernovae.
Key words: stars: abundances -- galaxies: Magellanic Clouds -- Galaxy: abundances -- galaxies: evolution
© ESO 2008