APOGEE [C/N] Abundances across the galaxy: Migration and infall from red giant ages

Sten Hasselquist, Jon A. Holtzman, Matthew Shetrone, Jamie Tayar, David H. Weinberg, Diane Feuillet, Katia Cunha, Marc H. Pinsonneault, Jennifer A. Johnson, Jonathan Bird, Timothy C. Beers, Ricardo Schiavon, Ivan Minchev, J. G. Fernández-Trincado, D. A. Garciá-Hernández, Christian Nitschelm, Olga Zamora

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


We present [C/N]-[Fe/H] abundance trends from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment survey, Data Release 14 (DR14), for red giant branch stars across the Milky Way (3 kpc < R < 15 kpc). The carbon-to-nitrogen ratio (often expressed as [C/N]) can indicate the mass of a red giant star, from which an age can be inferred. Using masses and ages derived by Martig et al., we demonstrate that we are able to interpret the DR14 [C/N]-[Fe/H] abundance distributions as trends in age-[Fe/H] space. Our results show that an anticorrelation between age and metallicity, which is predicted by simple chemical evolution models, is not present at any Galactic zone. Stars far from the plane ( kpc) exhibit a radial gradient in [C/N] (∼-0.04 dex kpc -1 ). The [C/N] dispersion increases toward the plane (σ [C/N] = 0.13 at kpc to σ [C/N] = 0.18 dex at |Z| < 0.5 kpc). We measure a disk metallicity gradient for the youngest stars (age < 2.5 Gyr) of-0.060 dex kpc -1 from 6 to 12 kpc, which is in agreement with the gradient found using young CoRoGEE stars by Anders et al. Older stars exhibit a flatter gradient (-0.016 dex kpc -1 ), which is predicted by simulations in which stars migrate from their birth radii. We also find that radial migration is a plausible explanation for the observed upturn of the [C/N]-[Fe/H] abundance trends in the outer Galaxy, where the metal-rich stars are relatively enhanced in [C/N].

Original languageEnglish (US)
Article number181
JournalAstrophysical Journal
Issue number2
StatePublished - Feb 1 2019
Externally publishedYes


  • Galaxy: Abundances
  • Galaxy: Disk
  • Galaxy: Evolution

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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