arXiv:astro-ph/0509344v1 13 Sep 2005 esa eeto fadafglx enn in remnant contro- galaxy dwarf still a the of to detection versial associated been al. has et Crane 2003) 2002; Stellar al. et Anticenter Newberg the see (Galactic Structure, like structure GASS tidal galaxies as the known major recently, More of Way. Milky evolution role the important an in play showed still Halo clearly galaxies the dwarf 2003) subse- how al. in et the debris Majewski tidal e.g. and (see its 1995), of of detection al. et discovery quent (Ibata the dSph particular, Sgr In formed. should galaxies have major which “build- of relic out blocks” the ing constitute to since believed galaxies are importance they dwarf increasing an Group acquired Local have years, recent In Introduction 1. 282 75, Vol. S.A.It. Mem. edo Send c At2004 SAIt ff ezn7–Glx:goua lses niiul aoa 1 Palomar individual: clusters: globular Galaxy: Galaxy: – – abundances 7 Terzan Galaxies: – CMa individual: Galaxies: aebe eie o pt 3eeet rmOye oEuropiu words. to Key Oxygen from elements 23 to up for derived been have vrest Ca.1 G tr eeaaye nteSrdSph me Sgr candidate CMa the three in with analyzed together dSph 7, were (Sgr Terzan stars globular Galaxy ated RGB Spheroidal 12 Dwarf (CMa). Sagittarius Overdensity the in dances 4 3 2 1 Abstract. .Sbordone L. rn eussto requests print nvri` iRm TrVraa,Rm,Italy e-mail: Rome, Vergata”, “Tor 2 Italy Roma Roma, Universit`a di di Astronomico Osservatorio Chile – Santiago, INAF Observatory, Southern European Italy – Trieste, ESO di Astronomico Osservatorio – INAF [email protected] esmaieterslso u non netgto fthe of investigation ongoing our of results the summarize We tr:audne tr:amshrs–Glxe:individ Galaxies: – atmospheres Stars: – abundances Stars: 1 , .Sbordone L. : 3 .Bonifacio P. 1 .Marconi G. ewe . n .) ufraudne for abundances Sulfur 1.3). and 0.8 between broee l 20 )w nlz Terzan 5 (T analyze In stars we (2000). 7 B) (2005 al. al. et et Bonifacio Sbordone in has presented elements 21 for been analysis an them of two For oiai ta.(04 o 2Srdp main dSph Sgr (T 12 stars for body (2004) al. et for Bonifacio results far, and So Iron Europium. to elements 23 Oxygen to from up stars, for abundances RGB deriving high and of analyzing spectra by VLT-UVES 7, resolution associated chemical Terzan the the in cluster and globular on dSph study Sgr in a abundances conducting are We 7 Terzan and dSph Sgr 2. al. et Bellazzini 2004). al. 2004; et Momany al. 2004; et Martin (see CMa 2 .Zaggia S. f f e α aay abundances Galaxy: – 2 lmnshv enpbihdin published been have elements ewe 95ad42 ,log K, 4421 and 3945 between lblrcutr:individual: clusters: globular f f e br.Dtie abundances Detailed mbers. Memorie n nteCnsMajor Canis the in and ) m. 1 ∼ n .Buonanno R. and ls5i h associ- the in 5 plus , 90Kadlog and K 4900 della a:Srdp – dSph Sgr ual: hmclabun- chemical g 4 ∼ 2.5). g Sbordone et al.: Abundances in Sgr and CMa 283 three of the Ter 7 stars have been presented gram based on VLT-FLAMES spectra, to study in Caffau et al. (2005). In all cases (except in the chemical abundances of CMa candidate Bonifacio et al. 2000), we have employed our member stars. In Sbordone et al. (2005 A) we Linux-ported version of the ATLAS-WIDTH- present the results on the three UVES stars SYNTHE suite (Kurucz 1993; Sbordone et al. that appeared suitable as CMa members, an- 2004; Sbordone 2005 C) to compute stellar at- alyzed with the same techniques described mosphere models and spectral syntheses, and above. Based on chemical abundances, one of to derive abundances. them is most likely a MW interloper, a sec- The studied stars in the Sgr dSph main ond one is of uncertain origin, while the third body show high metallicity ([Fe/H] between one shows a rather peculiar abundance pattern -0.8 and solar) and an undersolar [α/Fe] ra- that makes it unlikely to have originated inside tio, decreasing with increasing metallicity. Sgr the MW. It is a metal rich ([Fe/H]=0.15) sub- dSph appears to fall on the same [Fe/H] vs giant (Te f f =5367 K, log g=3.5), showing again [α/Fe] sequence with the other LG dSph, popu- underabundant α elements, high La, Ce and lating the Fe-rich, α-poor end of the sequence. Nd abundance, but, at odds with what we find This indicates that a prolonged albeit slow star in Sgr dSph, a significant Cu overabundance formation has taken place in the galaxy, a fact ([Cu/Fe]=0.25). The radial velocity of this star, confirmed also by the very young age of the also, appears to be the one that satisfies better studied population (age < 2 GYr). We looked the reported dynamics of the CMa overdensity. for traces of interstellar gas in Sgr dSph, to support for such a recent star formation, find- ing only little traces of ISM (see Monai et al. References 2005). Also the other studied elements present Bellazzini, M., Ferraro, F. R., & Ibata, R. 2003, many significant departures from solar ratios, AJ, 125, 188 (2003) with underabundant Na, Al and Sc, deficient Bellazzini, M., et al., 2004, MNRAS, 354, Ni, Cu and Zn, and strongly overabundant La, 1263 Ce and Nd. The five Ter 7 stars appear to Bonifacio, P., et al., 2000, A&A, 359, 663 share the same “chemical signature”, showing Bonifacio, P., et al. 2004, A&A, 414, 503 a mean [Fe/H]¯-0.59 and solar [α/Fe]. Caffau, E., Bonifacio, P., Faraggiana, R., & The chemical pattern displayed by the Sbordone, L. 2005, A&A, 436, L9 young Sgr dSph population can be used to Crane, J. D., et al., 2003, ApJ, 594, L119 probe stellar populations, now belonging to the Cohen, J. G. 2004, AJ, 127, 1545 Milky Way (MW), to verify if they formed in- Ibata, R. A., Gilmore, G., & Irwin, M. J. 1995, side the Sgr dSph system. A striking example MNRAS, 277, 781 of this is Palomar 12, a young MW globular Kurucz R. L., 1993, CDROM 13, 18 cluster, which abundances have been measured Majewski, et al., 2003, ApJ, 599, 1082 by Cohen (2004). This cluster was already sus- Martin, N. F., et al., 2004, MNRAS, 348, 12 pected to have been tidally stripped from Sgr Momany, Y., et al., 2004, A&A, 421, L29 dSph (e. g. Bellazzini et al. 2003). Actually, Monai, S., Bonifacio, P., & Sbordone, L. 2005, Pal 12 chemical pattern appears to strikingly A&A, 433, 241 reproduce the one we find in Sgr dSph, even in Newberg, H. J., et al. 2002, ApJ, 569, 245 the most significant departures from the solar Sbordone, L., Bonifacio, P., Castelli, F., & ratios (such as α elements, Al, Ni, Cu, Zn, La, Kurucz, R. L. 2004, MSAIS, 5, 93 Ce...), thus leading to consider essentially sure Sbordone, L., et al., 2005, A&A, 430, L13 its origin inside the Sgr dSph system. (2005 A) Sbordone, L., et al., 2005, A&A, 437, 905 (2005 B) 3. The CMa overdensity Sbordone, L. 2005, MSAIS, ?, in press (2005 Shortly after the detection of the CMa over- C) density, we undertook an exploratory pro-