Chemical Abundances in NGC 5024 (M53): A Mostly First Generation Globular Cluster

Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

doi:10.3847/0004-637x/824/1/5

Cited by 31 publications

(48 citation statements)

References 50 publications

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“…Our favourite option is the former, which is compatible with the large error bars of magnesium, relative to the overall Mg spread observed. This understanding is in agreement with the studies by Boberg et al (2016), who suggest that SG stars in M53 formed from gas diluted with pristine matter, and by Caloi & D'Antona (2011), that, based on the analysis of the HB, concluded that only a small helium spread, δY ∼ 0.04, is present, thus ruling out the existence of a purely AGB contaminated stellar component. Concerning the bottom-right panel of Fig.…”

Section: M53: a Cluster At The Edgesupporting

confidence: 91%

A view of the H-band light-element chemical patterns in globular clusters under the AGB self-enrichment scenario

Dell’Agli

García-Hernández

Ventura

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We discuss the self-enrichment scenario by AGB stars for the formation of multiple populations in globular clusters (GCs) by analyzing data set of giant stars observed in 9 Galactic GCs, covering a wide range of metallicities and for which the simultaneous measurements of C, N, O, Mg, Al, Si are available. To this aim we calculated 6 sets of AGB models, with the same chemical composition as the stars belonging to the first generation of each GC. We find that the AGB yields can reproduce the set of observations available, not only in terms of the degree of contamination shown by stars in each GC but, more important, also the observed trend with metallicity, which agrees well with the predictions from AGB evolution modelling. While further observational evidences are required to definitively fix the main actors in the pollution of the interstellar medium from which new generation of stars formed in GCs, the present results confirm that the gas ejected by stars of mass in the range 4 M M 8 M during the AGB phase share the same chemical patterns traced by stars in GCs.

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Section: M53: a Cluster At The Edgesupporting

confidence: 91%

A view of the H-band light-element chemical patterns in globular clusters under the AGB self-enrichment scenario

Dell’Agli

García-Hernández

Ventura

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…When compared to other methods of identifying multiple populations such as the Na-O anticorrelation (Carretta et al 2009a,b) and HST UV photometry (Milone et al 2017), we find that the CN band analysis classifies stars in common to these samples into the same populations. We do not find any of the outlying stars with enhanced CN and normal Na that have been discovered in M71, 47 Tuc, and M53 by Smith (2015a), Smith (2015b), and Boberg et al (2016a), respectively.…”

Section: Discussioncontrasting

confidence: 52%

Light Element Abundances and Multiple Populations in M10

Gerber¹,

Friel²,

Vesperini³

2018

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We present CN and CH band measurements for 137 RGB and AGB stars in the Galactic globular cluster M10. Our measurements come from low resolution spectroscopy taken with the Hydra spectrograph on the WIYN-3.5m telescope. We use these measurements to identify two populations of stars within the cluster, a CN-normal and CN-enhanced, and find that in our sample 60% of stars are CN-enhanced. Our large sample allows us to conduct a detailed analysis on the carbon and nitrogen abundances and the radial distribution of each population separately. Our analysis of the radial dependence shows that each population has the same radial distribution in the cluster, which is likely due to the cluster being dynamically evolved. We also compare our results to other methods of classifying multiple populations in globular clusters such as the Na-O anti-correlation and the HST pseudo-color magnitude diagrams. We find that these three methods of identifying multiple populations are in good agreement with each other for M10 and all lead to an estimate of the fraction of second generation stars approximately equal to 60%. Among AGB stars, when classified by the CN band, there appears to be a lack of second generation stars when compared to the RGB stars. However, when classified by [N/Fe], we find a similar 60% of AGB stars in the second generation. Finally, we use the measured carbon and nitrogen abundances in RGB stars to study the change of each element with magnitude as stars evolve up the RGB, comparing the results to globular clusters of similar metallicity, M3 and M13.

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“…Raising the separating value also brings the ratio of second generation stars from 60 % to 33 %, which comes closer to agreement with the ratio we find using δCN, the ratio found by Milone et al (2017) with HST photometry, and the ratio found by Bowman et al (2017) with narrow, CN-band photometry. Additionally with the exception of one HB star, we do not observe any CN-enhanced stars with normal [Na/Fe] values as reported by Smith et al (2013), Smith (2015a), and Boberg et al (2016) in M5, 47 Tuc, and M53, respectively.…”

Section: Discussionsupporting

confidence: 85%

Identifying Multiple Populations in M71 Using CN

Gerber

Friel

Vesperini

2020

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We have observed the CN features at ∼3800Å and 4120Å as well as the CH band at ∼4300Å for 145 evolved stars in the Galactic globular cluster M71 using the multi-object spectrograph, Hydra, on the WIYN-3.5m telescope. We use these measurements to create two δCN indices finding that both distributions are best fit by two populations, a CN-enhanced and CN-normal. We find that 42 ± 4% of the RGB stars in our sample are CN-enhanced. The percentage of CN-enhanced is 40 ± 13% for the AGB and 33 ± 9% for the HB stars, which suggests there are no missing second generation stars at these stages of stellar evolution. The two generations also separate in magnitude and color on the HB, which allows us to find the difference in He abundance between the two populations by fitting appropriate ZAHBs. The broad range of distances from the cluster's center covered by our sample allows us to study the dependence of the ratio of the number of first to second population stars on the distance from the cluster's center, and we find that this ratio does not vary radially and that the two populations are spatially mixed. Finally, we compare our identification of multiple populations with the classification based on the Na-O anti-correlation and the HST UV photometry, and we find good agreement with both methods.

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Chemical Abundances in NGC 5024 (M53): A Mostly First Generation Globular Cluster

Cited by 31 publications

References 50 publications

A view of the H-band light-element chemical patterns in globular clusters under the AGB self-enrichment scenario

A view of the H-band light-element chemical patterns in globular clusters under the AGB self-enrichment scenario

Light Element Abundances and Multiple Populations in M10

Identifying Multiple Populations in M71 Using CN

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