Journal
ASTRONOMICAL JOURNAL
Volume 149, Issue 5, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/0004-6256/149/5/153
Keywords
stars: abundances; stars: AGB and post-AGB; stars: chemically peculiar; stars: evolution
Categories
Funding
- Australian Research Council through DECRA Fellowship [DE140100598]
- PRIN MIUR Chemical and dynamical evolution of the Milky Way and Local Group Galaxies
- NASA through Hubble Fellowship from the Space Telescope Science Institute [HST-HF-51285.01]
- NASA [NAS5-26555]
- Physics Frontier Center/Joint Institute or Nuclear Astrophysics (JINA) [PHY 14-30152]
- Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE)
- US National Science Foundation
- National Science Foundation [AST-0907873, AST-1109888]
- Spanish Ministry of Economy and Competitiveness [AYA-2011-27754]
- Alfred P. Sloan Foundation
- National Science Foundation
- U.S. Department of Energy Office of Science
- [PHY 08-22648]
- Direct For Mathematical & Physical Scien
- Division Of Physics [1430152] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1109888] Funding Source: National Science Foundation
- Science and Technology Facilities Council [ST/M000966/1] Funding Source: researchfish
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We investigate the light-element behavior of red giant stars in northern globular clusters (GCs) observed by the SDSS-III Apache Point Observatory Galactic Evolution Experiment. We derive abundances of 9 elements (Fe, C, N, O, Mg, Al, Si, Ca, and Ti) for 428 red giant stars in 10 GCs. The intrinsic abundance range relative to measurement errors is examined, and the well-known C-N and Mg-Al anticorrelations are explored using an extreme-deconvolution code for the first time in a consistent way. We find that Mg and Al drive the population membership in most clusters, except in M107 and M71, the two most metal-rich clusters in our study, where the grouping is most sensitive to N. We also find a diversity in the abundance distributions, with some clusters exhibiting clear abundance bimodalities (for example M3 and M53) while others show extended distributions. The spread of Al abundances increases significantly as cluster average metallicity decreases as previously found by other works, which we take as evidence that low metallicity, intermediate mass AGB polluters were more common in the more metal-poor clusters. The statistically significant correlation of [Al/Fe] with [Si/Fe] in M15 suggests that Si-28 leakage has occurred in this cluster. We also present C, N, and O abundances for stars cooler than 4500 K and examine the behavior of A(C+N+O) in each cluster as a function of temperature and [Al/Fe]. The scatter of A(C+N+O) is close to its estimated uncertainty in all clusters and independent of stellar temperature. A(C+N+O) exhibits small correlations and anticorrelations with [Al/Fe] in M3 and M13, but we cannot be certain about these relations given the size of our abundance uncertainties. Star-to-star variations of alpha-element (Si, Ca, Ti) abundances are comparable to our estimated errors in all clusters.
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