The Open Cluster Chemical Analysis and Mapping Survey: Local Galactic Metallicity Gradient with APOGEE Using SDSS DR10

Frinchaboy, Peter M. and Thompson, Benjamin and Jackson, Kelly M. and O'Connell, Julia and Meyer, Brianne and Zasowski, Gail and Majewski, Steven R. and Chojnowksi, S. Drew and Johnson, Jennifer A. and Allende, Prieto Carlos and Beers, Timothy C. and Bizyaev, Dmitry and Brewington, Howard and Cunha, Katia and Ebelke, Garrett and Elia, Garc and Hearty, Frederick R. and Holtzman, Jon and Kinemuchi, Karen and Malanushenko, Elena and Malanushenko, Viktor and Marchante, Moses and Mészáros, Szabolcs and Muna, Demitri and Nidever, David L. and Oravetz, Daniel and Pan, Kaike and Schiavon, Ricardo P. and Schneider, Donald P. and Shetrone, Matthew (2013) The Open Cluster Chemical Analysis and Mapping Survey: Local Galactic Metallicity Gradient with APOGEE Using SDSS DR10. ASTROPHYSICAL JOURNAL LETTERS, 777 (1). ISSN 2041-8205

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Abstract

The Open Cluster Chemical Analysis and Mapping (OCCAM) Survey aims to produce a comprehensive, uniform, infrared-based dataset for hundreds of open clusters, and constrain key Galactic dynamical and chem- ical parameters from this sample. This first contribution from the OCCAM survey presents analysis of 141 members stars in 28 open clusters with high-resolution metallicities derived from a large uniform sample col- lected as part of the SDSS-III/Apache Point Observatory Galactic Evolution Experiment (APOGEE). This sample includes the first high-resolution metallicity measurements for 22 open clusters. With this largest ever uniformly observed sample of open cluster stars we investigate the Galactic disk gradients of both [M/H] and [α/M]. We find basically no gradient across this range in [α/M], but [M/H] does show a gradient for RGC < 10 kpc and a significant flattening beyond RGC = 10 kpc. In particular, whereas fitting a single linear trend yields an [M/H] gradient of −0.09 ± 0.03 dex kpc−1 — similar to previously measure gradients inside 13 kpc — by independently fitting inside and outside 10 kpc separately we find a significantly steeper gradient near the Sun (7.9 ≤ RGC ≤ 10) than previously found (−0.20 ± 0.08 dex kpc−1) and a nearly flat trend beyond 10 kpc (−0.02 ± 0.09 dex kpc−1).

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