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http://hdl.handle.net/20.500.12386/23339
Title: | The Gaia-ESO Survey: A globular cluster escapee in the Galactic halo | Authors: | Lind, K. Koposov, S. E. Battistini, C. Marino, A. F. Ruchti, G. Serenelli, A. Worley, C. C. Alves-Brito, A. Asplund, M. Barklem, P. S. Bensby, T. Bergemann, M. Blanco-Cuaresma, S. BRAGAGLIA, Angela Edvardsson, B. Feltzing, S. Gruyters, P. Heiter, U. Jofre, P. Korn, A. J. Nordlander, T. Ryde, N. Soubiran, C. Gilmore, G. RANDICH, Maria Sofia Ferguson, A. M. N. Jeffries, R. D. VALLENARI, Antonella Allende Prieto, C. PANCINO, ELENA Recio-Blanco, A. ROMANO, Donatella Smiljanic, R. BELLAZZINI, Michele DAMIANI, Francesco Hill, V. de Laverny, P. Jackson, R. J. Lardo, C. ZAGGIA, Simone |
Issue Date: | 2015 | Journal: | ASTRONOMY & ASTROPHYSICS | Number: | 575 | First Page: | L12 | Abstract: | A small fraction of the halo field is made up of stars that share the light element (Z ≤ 13) anomalies characteristic of second generation globular cluster (GC) stars. The ejected stars shed light on the formation of the Galactic halo by tracing the dynamical history of the clusters, which are believed to have once been more massive. Some of these ejected stars are expected to show strong Al enhancement at the expense of shortage of Mg, but until now no such star has been found. We search for outliers in the Mg and Al abundances of the few hundreds of halo field stars observed in the first eighteen months of the Gaia-ESO public spectroscopic survey. One halo star at the base of the red giant branch, here referred to as 22593757-4648029 is found to have [ Mg/Fe ] = -0.36 ± 0.04 and [ Al/Fe ] = 0.99 ± 0.08, which is compatible with the most extreme ratios detected in GCs so far. We compare the orbit of 22593757-4648029 to GCs of similar metallicity andfind it unlikely that this star has been tidally stripped with low ejection velocity from any of the clusters. However, both chemical and kinematic arguments render it plausible that the star has been ejected at high velocity from the anomalous GC ω Centauri within the last few billion years. We cannot rule out other progenitor GCs, because some may have disrupted fully, and the abundance and orbital data are inadequate for many of those that are still intact. <P />Based on data acquired by the Gaia-ESO Survey, programme ID 188.B-3002. Observations were made with ESO Telescopes at the La Silla Paranal Observatory.Appendix A is available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201425554/olm">http://www.aanda.org</A> <P /> | Acknowledgments: | This work was partly supported by the European Union FP7 programme through ERC grant number 320360, by the MICINN grant AYA2011-24704, by the ESF EUROCORES Program EuroGENESIS (MICINN grant EUI2009-04170), and by the Leverhulme Trust through grant RPG-2012-541. A.B., M.B., S.R., and D.R. acknowledge the support from INAF and Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR) in the form of the grant “Premiale VLT 2012” and PRIN MIUR 20102011 project “The Chemical and Dynamical Evolution of the Milky Way and Local Group Galaxies”, prot. 2010LY5N2T. The results presented here benefit from discussions held during the Gaia -ESO workshops and conferences supported by the European Science Foundation (ESF) through the GREAT Research Network Programme. We further acknowledge support from The Swedish Research Council (T.B. funded by grant No. 621-2009-3911), the Swedish Space Board (U.H. and A.J.K), and the Australian Research Council (M.A. funded by grant FL110100012). A.S. was funded by EPS2013-41268-R (MINECO) and No. 2014SGR-1458 (Generalitat de Catalunya). K.L. acknowledges the European Union FP7-PEOPLE-2012-IEF grant No. 328098. | URI: | http://hdl.handle.net/20.500.12386/23339 | URL: | https://www.aanda.org/articles/aa/abs/2015/03/aa25554-14/aa25554-14.html | ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/201425554 | Bibcode ADS: | 2015A&A...575L..12L | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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