Baade's window and APOGEE: Metallicities, ages, and chemical abundances

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Context. Baade's window (BW) is one of the most observed Galactic bulge fields in terms of chemical abundances. Owing to its low and homogeneous interstellar absorption it is considered the perfect calibration field for Galactic bulge studies. Aims. In the era of large spectroscopic surveys, calibration fields such as BW are necessary for cross calibrating the stellar parameters and individual abundances of the APOGEE survey. Methods. We use the APOGEE BW stars to derive the metallicity distribution function (MDF) and individual abundances for α-and iron-peak elements of the APOGEE ASPCAP pipeline (DR13), as well as the age distribution for stars in BW. Results. We determine the MDF of APOGEE stars in BW and find a remarkable agreement with that of the Gaia-ESO survey (GES). Both exhibit a clear bimodal distribution. We also find that the Mg-metallicity planes of the two surveys agree well, except for the metal-rich part ([Fe/H] > 0.1), where APOGEE finds systematically higher Mg abundances with respect to the GES. The ages based on the [C/N] ratio reveal a bimodal age distribution, with a major old population at ~ 10 Gyr, with a decreasing tail towards younger stars. A comparison of stellar parameters determined by APOGEE and those determined by other sources reveals detectable systematic offsets, in particular for spectroscopic surface gravity estimates. In general, we find a good agreement between individual abundances of O, Na, Mg, Al, Si, K, Ca, Cr, Mn, Co, and Ni from APOGEE with that of literature values. Conclusions. We have shown that in general APOGEE data show a good agreement in terms of MDF and individual chemical abundances with respect to literature works. Using the [C/N] ratio we found a significant fraction of young stars in BW.


  • M. Schultheis
  • A. Rojas-Arriagada
  • A. E. García Pérez
  • M. Hayden
  • G. Nandakumar
  • K. Cunha
  • C. Allende Prieto
  • J. A. Holtzman
  • T. C. Beers
  • D. Bizyaev
  • J. Brinkmann
  • R. Carrera
  • R. E. Cohen
  • D. Geisler
  • F. R. Hearty
  • J. G. Fernandez-Tricado
  • C. Maraston
  • D. Minnitti
  • C. Nitschelm
  • A. Roman-Lopes
  • D. P. Schneider
  • B. Tang
  • S. Villanova
  • G. Zasowski
  • S. R. Majewski
External organisations
  • Côte d'Azur Observatory
  • Millennium Institute of Astrophysics
  • Pontifical Catholic University of Chile
  • Instituto de Astrofísica de Canarias
  • University of La Laguna (ULL)
  • Laboratoire Joseph-Louis Lagrange
  • National Observatory Brazil
  • New Mexico State University
  • University of Notre Dame
  • Apache Point Observatory
  • Lomonosov Moscow State University
  • University of Concepción
  • Pennsylvania State University
  • Observatoire des Sciences de l'Univers de Besançon
  • University of Portsmouth
  • Andrés Bello National University
  • Vatican Observatory
  • University of Antofagasta
  • Universidad de La Serena
  • Johns Hopkins University
  • University of Utah
  • University of Virginia
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology


  • Galaxy: bulge, Galaxy: stellar content, Infrared: stars, Stars: abundances, Stars: fundamental parameters
Original languageEnglish
Article numberA14
JournalAstronomy and Astrophysics
Publication statusPublished - 2017 Apr 1
Publication categoryResearch
Externally publishedYes