Chemical Cartography with APOGEE: Multi-element Abundance Ratios

Research output: Contribution to journalArticle


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.


  • 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 Malanushenko
  • And 10 others
  • Szabolcs Mészáros
  • David L. Nidever
  • Christian Nitschelm
  • Kaike Pan
  • Hans Walter Rix
  • Jan Rybizki
  • Ricardo P. Schiavon
  • Donald P. Schneider
  • John C. Wilson
  • Olga Zamora
External organisations
  • Ohio State University
  • New Mexico State University
  • Vanderbilt University
  • University of Texas at Austin
  • University of Washington
  • Instituto de Astrofísica de Canarias
  • University of La Laguna (ULL)
  • Apache Point Observatory
  • INAF - Osservatorio Astronomico di Padova
  • University of Concepción
  • Space Telescope Science Institute
  • National Observatory Brazil
  • University of Arizona
  • University of Virginia
  • University of Atacama
  • University of Burgundy - Franche-Comté
  • Millennium Institute of Astrophysics
  • Eötvös Loránd University
  • Montana State University
  • University of Antofagasta
  • Max Planck Institute for Astronomy
  • Liverpool John Moores University
  • Pennsylvania State University
  • Pontifical Catholic University of Chile
  • National Optical Astronomy Observatory
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology


  • Galaxy: abundances, Galaxy: disk, nuclear reactions, nucleosynthesis, abundances, stars: abundances
Original languageEnglish
Article number102
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 2019 Mar 20
Publication categoryResearch