EDP Sciences
Free access
Issue A&A
Volume 465, Number 3, April III 2007
Page(s) 815 - 824
Section Galactic structure, stellar clusters, and populations
DOI http://dx.doi.org/10.1051/0004-6361:20066385



A&A 465, 815-824 (2007)
DOI: 10.1051/0004-6361:20066385

The exotic chemical composition of the Sagittarius dwarf spheroidal galaxy

L. Sbordone1, 2, 3, P. Bonifacio1, 2, 4, R. Buonanno5, 6, G. Marconi7, L. Monaco7, and S. Zaggia8

1  CIFIST Marie Curie Excellence Team, France
2  Observatoire de Paris, GEPI, 5 place Jules Janssen, 92195 Meudon, France
    e-mail: luca.sbordone@obspm.fr
3  INAF - Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Rome, Italy
4  INAF - Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
5  Università di Roma "Tor Vergata", via della Ricerca Scientifica 1, 00133 Rome, Italy
6  ASI Science Data Center, via Galileo Galilei, 00044 Frascati, Italy
7  ESO - European Southern Observatory, Alonso de Cordova, 3107 Santiago, Chile
8  INAF - Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padua, Italy

(Received 12 September 2006 / Accepted 29 November 2006)

Abstract
Context.The Sagittarius dwarf spheroidal galaxy is the nearest neighbor of the Milky Way. Moving along a short period quasi-polar orbit within the Halo, it is being destroyed by the tidal interaction with our Galaxy, losing its stellar content along a huge stellar stream.
Aims.We study the detailed chemical composition of 12 giant stars in the Sagittarius dwarf Spheroidal main body, together with 5 more in the associated globular cluster Terzan 7 , by means of high resolution VLT-UVES spectra.
Methods.Abundances are derived for up to 21 elements from O to Nd, by fitting lines EW or line profiles against ATLAS 9 model atmospheres and SYNTHE spectral syntheses calculated ad-hoc. Temperatures are derived from (V-I)0 or (B-V)0 colors and gravities from $\ion{Fe}{i}$ - $\ion{Fe}{ii}$ ionization equilibrium.
Results.The metallicity of the observed stars is between [Fe/H] = -0.9 and 0. We detected a highly peculiar "chemical signature", with undersolar $\alpha$ elements, Na, Al, Sc, V, Co, Ni, Cu, and Zn, among others, and overabundant La, Ce, and Nd. Many of these abundance ratios (in particular light-odd elements and iron peak ones) are strongly at odds with what is observed within the Milky Way, so they may be a very useful tool for recognizing populations originating within the Sagittarius dwarf. This can be clearly seen in the case of the globular Palomar 12 , which is believed to have been stripped from Sagittarius: the cluster shows precisely the same chemical "oddities", thus finally confirming its extragalactic origin.


Key words: stars: abundances -- stars: atmospheres -- Galaxy: abundances -- galaxies: dwarf -- galaxies: individual: Sgr dSph -- Galaxy: globular clusters: individual: Terzan 7



© ESO 2007

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.

Editor-in-Chief: T. Forveille
Letters Editor-in-Chief: J. Alves
Managing Editor: N. Aghanim

ISSN: 0004-6361 ; e-ISSN: 1432-0746
Frequency: 12 volumes per year
Published by: EDP Sciences

Mirror sites: CDS | EDP Sciences
  RSS feeds
© The European Southern Observatory (ESO)