Chemical Cartography with APOGEE: Multi-element Abundance Ratios

David H. Weinberg, Jon A. Holtzman, Sten Hasselquist, Jonathan C. Bird, Jennifer A. Johnson, Matthew Shetrone, Jennifer Sobeck, Carlos Allende Prieto, Dmitry Bizyaev, Ricardo Carrera, Roger E. Cohen, Katia Cunha, Garrett Ebelke, J. G. Fernandez-Trincado, D. A. Garcia-Hernández, Christian R. Hayes, Henrik Jönsson, Richard R. Lane, Steven R. Majewski, Viktor MalanushenkoSzabolcs Mészáros, David L. Nidever, Christian Nitschelm, Kaike Pan, Hans Walter Rix, Jan Rybizki, Ricardo P. Schiavon, Donald P. Schneider, John C. Wilson, Olga Zamora

Research output: Contribution to journalArticlepeer-review

88 Scopus citations


We map the trends of elemental abundance ratios across the Galactic disk, spanning R = 3-15 kpc and midplane distance |Z| = 0-2 kpc, for 15 elements in a sample of 20,485 stars measured by the SDSS/APOGEE survey (O, Na, Mg, Al, Si, P, S, K, Ca, V, Cr, Mn, Fe, Co, Ni). Adopting Mg rather than Fe as our reference element, and separating stars into two populations based on [Fe/Mg], we find that the median trends of [X/Mg] versus [Mg/H] in each population are nearly independent of location in the Galaxy. The full multi-element cartography can be summarized by combining these nearly universal median sequences with our measured metallicity distribution functions and the relative proportions of the low-[Fe/Mg] (high-α) and high-[Fe/Mg] (low-α) populations, which depend strongly on R and |Z|. We interpret the median sequences with a semi-empirical two-process model that describes both the ratio of core collapse and Type Ia supernova (SN Ia) contributions to each element and the metallicity dependence of the supernova yields. These observationally inferred trends can provide strong tests of supernova nucleosynthesis calculations. Our results lead to a relatively simple picture of abundance ratio variations in the Milky Way, in which the trends at any location can be described as the sum of two components with relative contributions that change systematically and smoothly across the Galaxy. Deviations from this picture and future extensions to other elements can provide further insights into the physics of stellar nucleosynthesis and unusual events in the Galaxys history.

Original languageEnglish (US)
Article number102
JournalAstrophysical Journal
Issue number1
StatePublished - Mar 20 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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