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

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 {sup 28}Si leakage has occurred in this cluster. We also presentmore » 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 α-element (Si, Ca, Ti) abundances are comparable to our estimated errors in all clusters.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ; ; ;  [5] ;  [6] ;  [7] ; ;  [8] ;  [9] ;  [10] ;  [11] ; ;  [12] ;  [13] ;  [14] ;  [15] ;
  1. ELTE Gothard Astrophysical Observatory, H-9704 Szombathely, Szent Imre Herceg st. 112 (Hungary)
  2. Department of Astrophysics, School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia)
  3. University of Texas at Austin, McDonald Observatory, Fort Davis, TX 79734 (United States)
  4. INAF-Osservatorio Astronomico di Padova, vicolo dell Osservatorio 5, I-35122 Padova (Italy)
  5. Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States)
  6. Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States)
  7. University of Arizona, Tucson, AZ 85719 (United States)
  8. Instituto de Astrofísica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain)
  9. Department of Astronomy, Indiana University, Bloomington, IN 47405 (United States)
  10. Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame, Notre Dame, IN 46556 (United States)
  11. Texas Christian University, Fort Worth, TX 76129 (United States)
  12. Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)
  13. New Mexico State University, Las Cruces, NM 88003 (United States)
  14. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)
  15. Astrophysics Research Institute, IC2, Liverpool Science Park, Liverpool John Moores University, 146 Brownlow Hill, Liverpool, L3 5RF (United Kingdom)
Publication Date:
OSTI Identifier:
22520202
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (Online); Journal Volume: 149; Journal Issue: 5; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ALUMINIUM; COMPARATIVE EVALUATIONS; COPPER; CORRELATIONS; ELEMENT ABUNDANCE; ERRORS; GALACTIC EVOLUTION; METALLICITY; RED GIANT STARS; SILICON 28; STAR CLUSTERS; STAR EVOLUTION; TEMPERATURE DEPENDENCE; VARIATIONS; VISIBLE RADIATION