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EXPLORING ANTICORRELATIONS AND LIGHT ELEMENT VARIATIONS IN NORTHERN GLOBULAR CLUSTERS OBSERVED BY THE APOGEE SURVEY

Meszaros, S and Martell, SL and Shetrone, M and Lucatello, S and Troup, NW and Bovy, J and Cunha, K and Garcia-Hernandez, DA and Overbeek, JC and Allende Prieto, C and Beers, TC and Frinchaboy, PM and Garcia Perez, AE and Hearty, FR and Holtzman, J and Majewski, SR and Nidever, DL and Schiavon, RP and Schneider, DP and Sobeck, JS and Smith, VV and Zamora, O and Zasowski, G (2015) EXPLORING ANTICORRELATIONS AND LIGHT ELEMENT VARIATIONS IN NORTHERN GLOBULAR CLUSTERS OBSERVED BY THE APOGEE SURVEY. ASTRONOMICAL JOURNAL, 149 (5). pp. 1-24. ISSN 0004-6256

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Abstract

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 28Si 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 a-element (Si, Ca, Ti) abundances are comparable to our estimated errors in all clusters.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: American Astronomical society
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Date Deposited: 11 Jan 2016 10:39
Last Modified: 07 Sep 2017 07:58
DOI or Identification number: 10.1088/0004-6256/149/5/153
URI: http://researchonline.ljmu.ac.uk/id/eprint/2565

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