APOGEE [C/N] Abundances Across the Galaxy: Migration and Infall from Red Giant Ages. (arXiv:1812.05092v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hasselquist_S/0/1/0/all/0/1">Sten Hasselquist</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Holtzman_J/0/1/0/all/0/1">Jon A. Holtzman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shetrone_M/0/1/0/all/0/1">Matthew Shetrone</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tayar_J/0/1/0/all/0/1">Jamie Tayar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Weinberg_D/0/1/0/all/0/1">David H. Weinberg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Feuillet_D/0/1/0/all/0/1">Diane Feuillet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cunha_K/0/1/0/all/0/1">Katia Cunha</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pinsonneault_M/0/1/0/all/0/1">Marc H. Pinsonneault</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Johnson_J/0/1/0/all/0/1">Jennifer A. Johnson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bird_J/0/1/0/all/0/1">Jonathan Bird</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Beers_T/0/1/0/all/0/1">Timothy C. Beers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schiavon_R/0/1/0/all/0/1">Ricardo Schiavon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Minchev_I/0/1/0/all/0/1">Ivan Minchev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fernandez_Trincado_J/0/1/0/all/0/1">J. G. Fern&#xe1;ndez-Trincado</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Garcia_Hernandez_D/0/1/0/all/0/1">D. A. Garc&#xed;a-Hern&#xe1;ndez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nitschelm_C/0/1/0/all/0/1">Christian Nitschelm</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zamora_O/0/1/0/all/0/1">Olga Zamora</a>

We present [C/N]-[Fe/H] abundance trends from the SDSS-IV Apache Point
Observatory Galactic Evolution Experiment (APOGEE) survey, Data Release 14
(DR14), for red giant branch stars across the Milky Way Galaxy (MW, 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 anti-correlation between age and metallicity, which is predicted by simple chemical evolution models, is not present at any Galactic zone. Stars far from the plane ($|$Z$|$ $>$ 1 kpc) exhibit a radial
gradient in [C/N] ($sim$ $-$0.04 dex/kpc). The [C/N] dispersion increases
toward the plane ($sigma_{[C/N]}$ = 0.13 at $|$Z$|$ $>$ 1 kpc to
$sigma_{[C/N]}$ = 0.18 dex at $|$Z$|$ $<$ 0.5 kpc). We measure a disk metallicity gradient for the youngest stars (age $<$ 2.5 Gyr) of $-$0.060 dex/kpc from 6 kpc to 12 kpc, which is in agreement with the gradient found using young CoRoGEE stars by Anders et al. Older stars exhibit a flatter gradient ($-$0.016 dex/kpc), 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].

We present [C/N]-[Fe/H] abundance trends from the SDSS-IV Apache Point
Observatory Galactic Evolution Experiment (APOGEE) survey, Data Release 14
(DR14), for red giant branch stars across the Milky Way Galaxy (MW, 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 anti-correlation between age and metallicity,
which is predicted by simple chemical evolution models, is not present at any
Galactic zone. Stars far from the plane ($|$Z$|$ $>$ 1 kpc) exhibit a radial
gradient in [C/N] ($sim$ $-$0.04 dex/kpc). The [C/N] dispersion increases
toward the plane ($sigma_{[C/N]}$ = 0.13 at $|$Z$|$ $>$ 1 kpc to
$sigma_{[C/N]}$ = 0.18 dex at $|$Z$|$ $<$ 0.5 kpc). We measure a disk
metallicity gradient for the youngest stars (age $<$ 2.5 Gyr) of $-$0.060
dex/kpc from 6 kpc to 12 kpc, which is in agreement with the gradient found
using young CoRoGEE stars by Anders et al. Older stars exhibit a flatter
gradient ($-$0.016 dex/kpc), 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].

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