Metallicity gradients in the Milky Way disk as observed by the segue survey

Judy Y. Cheng, Constance M. Rockosi, Heather L. Morrison, Ralph A. Schönrich, Young Sun Lee, Timothy C. Beers, Dmitry Bizyaev, Kaike Pan, Donald P. Schneider

Research output: Contribution to journalArticle

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Abstract

The observed radial and vertical metallicity distribution of old stars in the Milky Way disk provides a powerful constraint on the chemical enrichment and dynamical history of the disk system. We present the radial metallicity gradient, Δ[Fe/H]/ΔR, as a function of height above the plane, |Z|, using 7010 main-sequence turnoff stars observed by the Sloan Extension for Galactic Understanding and Exploration survey. The sample consists of mostly old thin and thick disk stars, with a minimal contribution from the stellar halo, in the region 6 kpc < R < 16kpc, 0.15 kpc < |Z| < 1.5kpc. The data reveal that the radial metallicity gradient becomes flat at heights |Z| > 1kpc. The median metallicity at large |Z| is consistent with the metallicities seen in outer disk open clusters, which exhibit a flat radial gradient at [Fe/H] ∼-0.5. We note that the outer disk clusters are also located at large |Z|; because the flat gradient extends to small R for our sample, there is some ambiguity in whether the observed trends for clusters are due to a change in R or |Z|. We therefore stress the importance of considering both the radial and vertical directions when measuring spatial abundance trends in the disk. The flattening of the gradient at high |Z| also has implications on thick disk formation scenarios, which predict different metallicity patterns in the thick disk. A flat gradient, such as we observe, is predicted by a turbulent disk at high redshift, but may also be consistent with radial migration, as long as mixing is strong. We test our analysis methods using a mock catalog based on the model of Schönrich & Binney, and we estimate our distance errors to be ∼25%. We also show that we can properly correct for selection biases by assigning weights to our targets.

Original languageEnglish (US)
Article number149
JournalAstrophysical Journal
Volume746
Issue number2
DOIs
StatePublished - Feb 20 2012

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metallicity
gradients
vertical distribution
history
trends
trend
stars
open clusters
main sequence stars
flattening
ambiguity
catalogs
halos
histories
test
measuring
method
analysis
chemical
estimates

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Cheng, J. Y., Rockosi, C. M., Morrison, H. L., Schönrich, R. A., Lee, Y. S., Beers, T. C., ... Schneider, D. P. (2012). Metallicity gradients in the Milky Way disk as observed by the segue survey. Astrophysical Journal, 746(2), [149]. https://doi.org/10.1088/0004-637X/746/2/149
Cheng, Judy Y. ; Rockosi, Constance M. ; Morrison, Heather L. ; Schönrich, Ralph A. ; Lee, Young Sun ; Beers, Timothy C. ; Bizyaev, Dmitry ; Pan, Kaike ; Schneider, Donald P. / Metallicity gradients in the Milky Way disk as observed by the segue survey. In: Astrophysical Journal. 2012 ; Vol. 746, No. 2.
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Cheng, JY, Rockosi, CM, Morrison, HL, Schönrich, RA, Lee, YS, Beers, TC, Bizyaev, D, Pan, K & Schneider, DP 2012, 'Metallicity gradients in the Milky Way disk as observed by the segue survey', Astrophysical Journal, vol. 746, no. 2, 149. https://doi.org/10.1088/0004-637X/746/2/149

Metallicity gradients in the Milky Way disk as observed by the segue survey. / Cheng, Judy Y.; Rockosi, Constance M.; Morrison, Heather L.; Schönrich, Ralph A.; Lee, Young Sun; Beers, Timothy C.; Bizyaev, Dmitry; Pan, Kaike; Schneider, Donald P.

In: Astrophysical Journal, Vol. 746, No. 2, 149, 20.02.2012.

Research output: Contribution to journalArticle

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Cheng JY, Rockosi CM, Morrison HL, Schönrich RA, Lee YS, Beers TC et al. Metallicity gradients in the Milky Way disk as observed by the segue survey. Astrophysical Journal. 2012 Feb 20;746(2). 149. https://doi.org/10.1088/0004-637X/746/2/149