Multiple Stellar Populations of Globular Clusters from Homogeneous Ca-CN Photometry. II. M5 (NGC 5904) and a New Filter System

Using our ingeniously designed new filter systems, we investigate multiple stellar populations of the red giant branch (RGB) and the asymptotic giant branch (AGB) in the globular cluster (GC) M5. Our results are the following. (1) Our index accurately traces nitrogen abundances in M5, while other co...

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Bibliographic Details
Published in:The Astrophysical journal 2017-07, Vol.844 (1), p.77
Main Author: Lee, Jae-Woo
Format: Article
Language:English
Subjects:
Abundance
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Asymptotic giant branch stars
ASYMPTOTIC SOLUTIONS
CALCIUM
CARBON NITRIDES
COMPARATIVE EVALUATIONS
ELEMENT ABUNDANCE
FILTERS
Globular clusters
HELIUM
HERTZSPRUNG-RUSSELL DIAGRAM
Iron
NITROGEN
PHOTOMETRY
Red giant stars
ROTATION
Sequences
SPATIAL DISTRIBUTION
STAR CLUSTERS
STARS
Stellar populations
STOCHASTIC PROCESSES
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Summary:Using our ingeniously designed new filter systems, we investigate multiple stellar populations of the red giant branch (RGB) and the asymptotic giant branch (AGB) in the globular cluster (GC) M5. Our results are the following. (1) Our index accurately traces nitrogen abundances in M5, while other color indices fail to do so. (2) We find bimodal CN distributions in both RGB and AGB sequences, with number ratios between CN-weak (CN-w) and CN-strong (CN-s) of n (CN-w): n (CN-s) = 29:71 (±2) and 21:79 (±7), respectively. (3) We also find a bimodal photometric [N/Fe] distribution for M5 RGB stars. (4) Our –[O/Fe] and –[Na/Fe] relations show clear discontinuities between the two RGB populations. (5) Although small, the RGB bump of CN-s is slightly brighter,  = 0.07 ± 0.04 mag. If real, the difference in the helium abundance becomes  = 0.028 ± 0.016, in the sense that CN-s is more helium enhanced. (6) Very similar radial but different spatial distributions with comparable center positions are found for the two RGB populations. The CN-s RGB and AGB stars are more elongated along the NW–SE direction. (7) The CN-s population shows a substantial net projected rotation, while that of the CN-w population is nil. (8) Our results confirm the deficiency of CN-w AGB stars previously noted by others. We show that it is most likely due to stochastic truncation in the outer part of the cluster. Finally, we discuss the formation scenario of M5.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aa7b8c