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Analysis and calibration of Ca ii triplet spectroscopy of red giant branch stars from VLT/FLAMES observations

Battaglia, G. ; Irwin, M. ; Tolstoy, E. ; Hill, V. ; Helmi, A. ; Letarte, B. ; Jablonka, P.

In: Monthly Notices of the Royal Astronomical Society, 2008, vol. 383, no. 1, p. 183-199

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    Title
    • Analysis and calibration of Ca ii triplet spectroscopy of red giant branch stars from VLT/FLAMES observations
    Author
    • Battaglia, G.. Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, the Netherlands
    • Irwin, M.. Institute of Astronomy, Madingley Road, Cambridge CB3 0HA
    • Tolstoy, E.. Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, the Netherlands
    • Hill, V.. GEPI, Observatoire de Paris, CNRS, Universit Paris Diderot; Place Jules Janssen 92190 Meudon, France
    • Helmi, A.. Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, the Netherlands
    • Letarte, B.. Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, the Netherlands
    • Jablonka, P.. Observatoire de Genève, Laboratoire d'Astrophysique de l'Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1290 Sauverny, Switzerland
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:293563
    Summary
    We demonstrate that low-resolution Ca ii triplet (CaT) spectroscopic estimates of the overall metallicity ([Fe/H]) of individual red giant branch (RGB) stars in two nearby dwarf spheroidal galaxies (dSphs) agree to ±0.1-0.2 dex with detailed high-resolution spectroscopic determinations for the same stars over the range −2.5 < [Fe/H] < −0.5. For this study, we used a sample of 129 stars observed in low- and high-resolution modes with VLT/FLAMES in the Sculptor and Fornax dSphs. We also present the data-reduction steps we used in our low-resolution analysis and show that the typical accuracy of our velocity and CaT [Fe/H] measurement is ∼2 km s−1 and 0.1 dex, respectively. We conclude that CaT-[Fe/H] relations calibrated on globular clusters can be applied with confidence to RGB stars in composite stellar populations over the range −2.5 < [Fe/H] < −0.5