@article{fc8b8549a39e40ca89b4340d62c5fcd2,
title = "Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns",
abstract = "We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] -1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similar metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution.",
keywords = "globular clusters: general, stars: abundances, stars: Population II, structure",
author = "Fern{\'a}ndez-Trincado, {J. G.} and O. Zamora and Garcia-Hern{\'a}ndez, {D. A.} and Diogo Souto and F. Dell'Agli and Schiavon, {R. P.} and D. Geisler and B. Tang and S. Villanova and Sten Hasselquist and Mennickent, {R. E.} and Katia Cunha and M. Shetrone and Prieto, {Carlos Allende} and K. Vieira and G. Zasowski and J. Sobeck and Hayes, {C. R.} and Majewski, {S. R.} and Placco, {V. M.} and Beers, {T. C.} and Schleicher, {D. R.G.} and Robin, {A. C.} and Sz M{\'e}sz{\'a}ros and T. Masseron and P{\'e}rez, {Ana E.Garcia} and F. Anders and A. Meza and A. Alves-Brito and R. Carrera and D. Minniti and Lane, {R. R.} and E. Fern{\'a}ndez-Alvar and E. Moreno and B. Pichardo and A. P{\'e}rez-Villegas and M. Schultheis and A. Roman-Lopes and Fuentes, {C. E.} and C. Nitschelm and P. Harding and D. Bizyaev and K. Pan and D. Oravetz and A. Simmons and Ivans, {Inese I.} and S. Blanco-Cuaresma and J. Hern{\'a}ndez and J. Alonso-Garcia and O. Valenzuela and J. Chanam{\'e}",
note = "Funding Information: We thank Paolo Ventura and Marco Limongi for useful discussions. We are grateful to the referee for a prompt and constructive report. J.G.F.-T. is especially grateful for the technical expertise and assistance provided by the Instituto de Astrof{\'i}sica de Canarias (IAC). J.G.F.-T., D.G., and B.T. gratefully acknowledge support from the Chilean BASAL Centro de Excelencia en Astrof{\'i}sica y Tecnolog{\'i}as Afines (CATA) grant PFB-06/2007. S.V. gratefully acknowledges the support provided by Fondecyt reg. No. 1170518. D.A.G.H. was funded by the Ram{\'o}n y Cajal fellowship number RYC-2013-14182. D.A.G.H., O.Z., and F.D. acknowledge support provided by the Spanish Ministry of Economy and Competitiveness (MINECO) under grant AYA-2014-58082-P. S.M. has been supported by the Premium Postdoctoral Research Program of the Hungarian Academy of Sciences, and by the Hungarian NKFI grants K-119517 of the Hungarian National Research, Development and Innovation Office. D.M. is also supported by FONDECYT No. 1170121 and by the Ministry of Economy, Development, and Tourismʼs Millennium Science Initiative through grant IC120009, awarded to the Millennium Institute of Astrophysics (MAS). E.M, B.P., and A.P.V. acknowledge support from UNAM/PAPIIT grants IN105916 and IN114114. A.R.L. thanks partial financial support from the FONDECYT REGULAR project 1170476. Funding Information: Funding for the GravPot16 software has been provided by the Centre national d{\textquoteright}{\'e}tudes spatiales (CNES) through grant 0101973 and the UTINAM Institute of the Universit{\'e} de Franche-Comt{\'e} supported by the Region de Franche-Comt{\'e} and Institut des Sciences de l{\textquoteright}Univers (INSU). Funding Information: Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is www.sdss.org. SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrof{\`i}sicade Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut f{\"u}r Astrophysik Potsdam (AIP), Max-Planck-Institut f{\"u}r Astronomie (MPIA Heidelberg), Max-Planck-Institut f{\"u}r Astrophysik (MPA Garching), Max-Planck-Institut f{\"u}r Extraterrestrische Physik (MPE), National Astronomical Observatory of China, New Mexico State University, New York University, University of Notre Dame, Observat{\'o}rio Nacional/MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Aut{\'o}n-oma de M{\'e}xico, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University, and Yale University.",
year = "2017",
month = sep,
day = "1",
doi = "10.3847/2041-8213/aa8032",
language = "English",
volume = "846",
journal = "Astrophysical Journal Letters",
issn = "2041-8205",
publisher = "IOP Publishing Ltd.",
number = "1",
}