Chemical cartography with apogee: Large-scale mean metallicity maps of the milky way disk

Michael R. Hayden, Jon A. Holtzman, Jo Bovy, Steven R. Majewski, Jennifer A. Johnson, Carlos Allende Prieto, Timothy C. Beers, Katia Cunha, Peter M. Frinchaboy, Ana E. García Pérez, Léo Girardi, Fred R. Hearty, Young Sun Lee, David Nidever, Ricardo P. Schiavon, Katharine J. Schlesinger, Donald P. Schneider, Mathias Schultheis, Matthew Shetrone, Verne V. SmithGail Zasowski, Dmitry Bizyaev, Diane Feuillet, Sten Hasselquist, Karen Kinemuchi, Elena Malanushenko, Viktor Malanushenko, Robert O'Connell, Kaike Pan, Keivan Stassun

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101 Scopus citations

Abstract

We present Galactic mean metallicity maps derived from the first year of the SDSS-III APOGEE experiment. Mean abundances in different zones of projected Galactocentric radius (0 < R < 15 kpc) at a range of heights above the plane (0 < |z| < 3 kpc), are derived from a sample of nearly 20,000 giant stars with unprecedented coverage, including stars in the Galactic mid-plane at large distances. We also split the sample into subsamples of stars with low- and high-[α/M] abundance ratios. We assess possible biases in deriving the mean abundances, and find that they are likely to be small except in the inner regions of the Galaxy. A negative radial metallicity gradient exists over much of the Galaxy; however, the gradient appears to flatten for R < 6 kpc, in particular near the Galactic mid-plane and for low-[α/M] stars. At R > 6 kpc, the gradient flattens as one moves off the plane, and is flatter at all heights for high-[α/M] stars than for low-[α/M] stars. Alternatively, these gradients can be described as vertical gradients that flatten at larger Galactocentric radius; these vertical gradients are similar for both low- and high-[α/M] populations. Stars with higher [α/M] appear to have a flatter radial gradient than stars with lower [α/M]. This could suggest that the metallicity gradient has grown steeper with time or, alternatively, that gradients are washed out over time by migration of stars.

Original languageEnglish (US)
Article number116
JournalAstronomical Journal
Volume147
Issue number5
DOIs
StatePublished - May 2014

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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