EDP Sciences
Free access
Issue
A&A
Volume 430, Number 1, January IV 2005
Page(s) L13 - L16
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200400118


A&A 430, L13-L16 (2005)
DOI: 10.1051/0004-6361:200400118

Letter

UVES observations of the Canis Major overdensity

L. Sbordone1, 2, P. Bonifacio3, G. Marconi1, S. Zaggia3 and R. Buonanno2

1  ESO - European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago de Chile
    e-mail: lsbordon@eso.org
2  Universitá di Roma "Tor Vergata", via Della Ricerca Scientifica 2, Roma, Italy
3  INAF - Osservatorio Astronomico di Trieste, via G. B. Tiepolo, Trieste, Italy

(Received 21 October 2004 / Accepted 2 December 2004)

Abstract
We present the first detailed chemical abundances for three giant stars which are candidate members of the Canis Major overdensity, obtained by using FLAMES-UVES at VLT. The stars, in the background of the open cluster NGC 2477 , have radial velocities compatible with a membership to this structure. However, due to Galactic disc contamination, radial velocity by itself is unable to firmly establish membership. The metallicities span the range $\rm -0.5\la [Fe/H] \la +0.1$. Assuming that at least one of the three stars is indeed a member of CMa implies that this structure has undergone a high level of chemical processing, comparable to that of the Galactic disc. The most metal-rich star of the sample, EIS 6631 , displays several abundance ratios which are remarkably different from those of Galactic stars: ${\rm [\alpha/Fe]} \sim -0.2$, ${\rm [Cu/Fe]} \sim +0.25$, ${\rm [La/Fe]} \sim +0.6$, ${\rm [Ce/Fe]} \sim +0.8$ and ${\rm [Nd/Fe]}\sim +0.6$. These ratios make it likely that this star was formed in an external galaxy.


Key words: stars: abundances -- stars: atmospheres -- galaxies: abundances -- galaxies: evolution -- galaxies: dwarf

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© ESO 2005