The Search for Extremely Low-Metallicity Stars in Dwarf Galaxies Using the NIR Ca II Triplet

Creators: Starkenburg, Else; Hill, Vanessa; Tolstoy, Eline; González Hernández, J. I.; Irwin, Michael J.; Helmi, Amina; Boschman, L.; François, Patrick; Battaglia, Giuseppina; Jablonka, Pascale; Tafelmeyer, M.; Shetrone, Matthew D.; Venn, Kimberly A.; de Boer, T.

Others:: Kapteyn Astronomical Institute, University of Groningen; Observatoire de la Côte d'Azur (OCA) ; Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS); Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM); Institute of Astronomy, University of Cambridge (IoA); Galaxies, Etoiles, Physique, Instrumentation (GEPI) ; Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris ; Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS); Physique des Galaxies et Cosmologie ; Galaxies, Etoiles, Physique, Instrumentation (GEPI) ; Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris ; Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris ; Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS); Physique stellaire et galactique ; Galaxies, Etoiles, Physique, Instrumentation (GEPI) ; Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris ; Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris ; Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS); European Organization for Astronomical Research in the Southern Hemisphere (ESO); Ecole Polytechnique Fédérale de Lausanne (EPFL); McDonald Observatory, University of Texas; Department of Physics and Astronomy, University of Victoria; Koleva; M.; Prugniel; Ph.; Vauglin; I.

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The NIR Ca II triplet has proven to be an important tool for quantitative spectroscopy. Here we present results of synthetic spectral analysis for the Ca II triplet for low-metallicity red giant stars, combined with observational data. Our results start to deviate strongly from the widely-used and linear empirical calibrations below [Fe/H] = -2. We provide a new calibration for Ca II triplet studies which is valid down until [Fe/H] = -4 and apply this new calibration to current data sets. We suggest that the classical dwarf galaxies are not so devoid of extremely low-metallicity stars as was previously thought and discuss preliminary results and possibilities for follow-up observations of these extremely low-metallicity candidates.

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The Search for Extremely Low-Metallicity Stars in Dwarf Galaxies Using the NIR Ca II Triplet

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