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|Title:||Chemical abundances of giant stars in <ASTROBJ>NGC 5053</ASTROBJ> and <ASTROBJ>NGC 5634</ASTROBJ>, two globular clusters associated with the Sagittarius dwarf spheroidal galaxy?||Authors:||Sbordone, L.
Moni Bidin, C.
|Issue Date:||2015||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||579||First Page:||A104||Abstract:||Context. The tidal disruption of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) is producing the most prominent substructure in the Milky Way (MW) halo, the Sagittarius Stream. Aside from field stars, it is suspected that the Sgr dSph has lost a number of globular clusters (GC). Many Galactic GC are thought to have originated in the Sgr dSph. While for some candidates an origin in the Sgr dSph has been confirmed owing to chemical similarities, others exist whose chemical composition has never been investigated. <BR /> Aims: <ASTROBJ>NGC 5053</ASTROBJ> and <ASTROBJ>NGC 5634</ASTROBJ> are two of these scarcely studied Sgr dSph candidate-member clusters. To characterize their composition we analyzed one giant star in <ASTROBJ>NGC 5053</ASTROBJ>, and two in <ASTROBJ>NGC 5634</ASTROBJ>. <BR /> Methods: We analyze high-resolution and signal-to-noise spectra by means of the MyGIsFOS code, determining atmospheric parameters and abundances for up to 21 species between O and Eu. The abundances are compared with those of MW halo field stars, of unassociated MW halo globulars, and of the metal-poor Sgr dSph main body population. <BR /> Results: We derive a metallicity of [Fe ii/H] = -2.26 ± 0.10 for <ASTROBJ>NGC 5053</ASTROBJ>, and of [Fe i/H] = -1.99 ± 0.075 and -1.97 ± 0.076 for the two stars in <ASTROBJ>NGC 5634</ASTROBJ>. This makes <ASTROBJ>NGC 5053</ASTROBJ> one of the most metal-poor globular clusters in the MW. Both clusters display an α enhancement similar to the one of the halo at comparable metallicity. The two stars in <ASTROBJ>NGC 5634</ASTROBJ> clearly display the Na-O anticorrelation widespread among MW globulars. Most other abundances are in good agreement with standard MW halo trends. <BR /> Conclusions: The chemistry of the Sgr dSph main body populations is similar to that of the halo at low metallicity. It is thus difficult to discriminate between an origin of <ASTROBJ>NGC 5053</ASTROBJ> and <ASTROBJ>NGC 5634</ASTROBJ> in the Sgr dSph, and one in the MW. However, the abundances of these clusters do appear closer to that of Sgr dSph than of the halo, favoring an origin in the Sgr dSph system. <P />Appendix A is available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201425509/olm">http://www.aanda.org</A>Atomic data are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://220.127.116.11) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/vol/A104">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/vol/A104</A>||Acknowledgments:||Support for L.S. and S.D. is provided by Chile’s Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. C.M.B. gratefully acknowledges the support provided by Fondecyt reg. No. 1150060. S.V. gratefully acknowledges the support provided by Fondecyt reg. No. 1130721. M.B. acknowledges financial support from PRIN MIUR 2010-2011, project “The Chemical and Dynamical Evolution of the Milky Way and Local Group Galaxies”, prot. 2010LY5N2T. D.G. gratefully acknowledges support from the Chilean BASAL Centro de Excelencia en Astrofísica y Tecnologías Afines (CATA) grant PFB-06/2007. E.C. is grateful to the FONDATION MERAC for funding her fellowship. Based in part on data collected at Subaru Telescope and obtained from the SMOKA, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan. This research has made use of NASA’s Astrophysics Data System, and of the VizieR catalogue access tool, CDS, Strasbourg, France||URI:||http://hdl.handle.net/20.500.12386/23338||URL:||https://www.aanda.org/articles/aa/abs/2015/07/aa25509-14/aa25509-14.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201425509||Bibcode ADS:||2015A&A...579A.104S||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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