Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)★

Yong, David; Roederer, Ian U.; Grundahl, F.; Costa, G. S. Da; Karakas, Amanda I.; Norris, John E.; Aoki, Wako; Fishlock, Cherie; Marino, A. F.; Milone, A. P.; Shingles, Luke J.

doi:10.1093/mnras/stu806

Cited by 143 publications

(171 citation statements)

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“…Although NGC 6273 is only at a distance of ∼9 kpc from the Sun (e.g., Piotto et al 1999), the large and highly variable reddening complicate both cluster RGB target selection and the interpretation of its color- 8 The term "iron-complex" refers to any globular cluster exhibiting a significant (0.10 dex) [Fe/H] dispersion when measured from high resolution spectra. We have adopted this term in order to avoid confusing the word "anomalous," which can refer to either a cluster with a metallicity dispersion (e.g., Marino et al 2015) or a sub-population with peculiar chemistry residing in a cluster (e.g., Pancino et al 2000;Yong et al 2014). We note that clusters with both [Fe/H] and s-process abundance spreads have also been referred to as "s-Fe-anomalous" .…”

Section: Observations and Target Selectionmentioning

confidence: 99%

“…Combining the information from Figures 10 and 15 indicates that in all of the iron-complex clusters included here the increase in [La/Eu] is due to almost pure s-process enrichment. Previous work on iron-complex clusters such as M2 (Lardo et al 2013;Yong et al 2014), M22 (Marino et al 2009(Marino et al , 2011b, and NGC 5286 suggested that each may be decomposed into at least two populations: a low The similar heavy element abundance patterns observed for many iron-complex clusters makes it tempting to speculate that all of them formed through the same basic process. However, just as both normal and iron-complex clusters exhibit similar light element abundance variations but can have very different heavy element distributions, the similar s-process abundances of the iron-complex clusters could be a red herring.…”

Section: Comparison With Other "Iron-complex"mentioning

confidence: 99%

“…The massive globular cluster omega Centauri (ω Cen) is the best known and most extreme object from this group, and has been demonstrated by multiple authors to possess: a very blue HB, a range in [Fe/H] that spans about a factor of 100, at least five distinct main stellar populations (each with its own set of primordial, intermediate, and extreme stars), and a strong correlation between metallicity and elements such as Ba and La that are likely produced by the s-process (e.g., Norris & Da Costa 1995;Suntzeff & Kraft 1996;Lee et al 1999;Smith et al 2000;Bellini et al 2010;Johnson & Pilachowski 2010;D'Orazi et al 2011;Marino et al 2011a;Pancino et al 2011;Villanova et al 2014). Less extreme examples also include M22, M2, M54, NGC 1851, NGC 5286, NGC 5824, and Terzan 5 (M22: e.g., Hesser et al 1977;Pilachowski et al 1982;Lehnert et al 1991;Marino et al 2009Marino et al , 2011bMarino et al , 2013Da Costa et al 2009;Roederer et al 2011;Alves-Brito et al 2012;M2: Piotto et al 2012;Lardo et al 2013;Yong et al 2014;Milone et al 2015;M54: e.g., Sarajedini & Layden 1995;Brown et al 1999;Siegel et al 2007;Bellazzini et al 2008;Carretta et al 2010a;NGC 1851: e.g., Yong & Grundahl 2008Milone et al 2009;Yong et al 2009Yong et al , 2015Zoccali et al 2009;Carretta et al 2010bCarretta et al , 2011…”

Section: Introductionmentioning

confidence: 99%

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A Spectroscopic Analysis of the Galactic Globular Cluster NGC 6273 (M19)

et al. 2015

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A combined effort utilizing spectroscopy and photometry has revealed the existence of a new globular cluster class. These "anomalous" clusters, which we refer to as "iron-complex" clusters, are differentiated from normal clusters by exhibiting large (0.10 dex) intrinsic metallicity dispersions, complex sub-giant branches, and correlated [Fe/H] and s-process enhancements. In order to further investigate this phenomenon, we have measured radial velocities and chemical abundances for red giant branch stars in the massive, but scarcely studied, globular cluster NGC 6273. The velocities and abundances were determined using high resolution (R ∼ 27,000) spectra obtained with the Michigan/ Magellan Fiber System (M2FS) and MSpec spectrograph on the Magellan-Clay 6.5 m telescope at Las Campanas Observatory. We find that NGC 6273 has an average heliocentric radial velocity of +144.49 km s −1 (σ = 9.64 km s

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Section: Observations and Target Selectionmentioning

confidence: 99%

Section: Comparison With Other "Iron-complex"mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Spectroscopic Analysis of the Galactic Globular Cluster NGC 6273 (M19)

et al. 2015

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“…1999;Gratton et al 2001;Bedin et al 2004;Norris 2004;Piotto et al 2005;Mackey & Broby Nielsen 2007;Lee et al 2009;Da Costa et al 2014;See Gratton et al 2012 for a recent review). Most of the investigated GCs in the Galaxy are observed to show anti-correlations between light elements (e.g., C, N, and O) of cluster members stars (e.g., Carretta et al 2009; C09) whereas only 8 GCs have been so far confirmed to have star-to-star abundance spreads in heavy elements (e.g., Yong et al 2014;Marino et al 2015). Extended main-sequence turn-offs (eMSTOs) and splits in main-sequence observed in the color magnitude diagrams (CMDs) of some LMC GCs (e.g., Mackey & Broby ⋆ E-mail: kenji.bekki@uwa.edu.au Nielsen 2007; Goudfrooij et al 2014;Milone et al 2016) can be possible evidence for the multiple stellar populations with different ages, though recent observations suggest that internal stellar rotation rather than age spreads could explain the physical properties of LMC clusters with eMSTOs (e.g., Bastian & De Mink 2009;Milone et al 2016;Li et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

Bekki¹

2017

Mon. Not. R. Astron. Soc.

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Most old globular clusters (GCs) in the Galaxy are observed to have internal chemical abundance spreads in light elements. We discuss a new GC formation scenario based on hierarchical star formation within fractal molecular clouds. In the new scenario, a cluster of bound and unbound star clusters ('star cluster complex', SCC) that have a power-law cluster mass function with a slope (β) of 2 is first formed from a massive gas clump developed in a dwarf galaxy. Such cluster complexes and β = 2 are observed and expected from hierarchical star formation. The most massive star cluster ('main cluster'), which is the progenitor of a GC, can accrete gas ejected from asymptotic giant branch (AGB) stars initially in the cluster and other low-mass clusters before the clusters are tidally stripped or destroyed to become field stars in the dwarf. The SCC is initially embedded in a giant gas hole created by numerous supernovae of the SCC so that cold gas outside the hole can be accreted onto the main cluster later. New stars formed from the accreted gas have chemical abundances that are different from those of the original SCC. Using hydrodynamical simulations of GC formation based on this scenario, we show that the main cluster with the initial mass as large as [2 − 5] × 10 5 M ⊙ can accrete more than 10 5 M ⊙ gas from AGB stars of the SCC. We suggest that merging of hierarchical star cluster complexes can play key roles in stellar halo formation around GCs and self-enrichment processes in the early phase of GC formation.

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“…Globular clusters (GCs) host mono-metallic 1 , almost coeval stellar populations that have been studied extensively, both ⋆ E-mail: angelou@mps.mpg.de 1 with a few exceptions, such as e.g., Omega Cenaturi (Johnson & Pilachowski 2010), M22 (Marino et al 2009), M54 (Carretta et al 2010a), M2 (Yong et al 2014) photometrically and spectroscopically. In spite of their multiple populations (see Gratton, Carretta & Bragaglia 2012), these systems offer well constrained tests for stellar evolution theory.…”

Section: Introductionmentioning

confidence: 99%

Diagnostics of stellar modelling from spectroscopy and photometry of globular clusters

Angelou

D’Orazi

Constantino

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We conduct a series of comparisons between spectroscopic and photometric observations of globular clusters and stellar models to examine their predictive power. Data from medium-to-high resolution spectroscopic surveys of lithium allow us to investigate first dredge-up and extra mixing in two clusters well separated in metallicity. Abundances at first dredge-up are satisfactorily reproduced but there is preliminary evidence to suggest that the models overestimate the luminosity at which the surface composition first changes in the lowest-metallicity system. Our models also begin extra mixing at luminosities that are too high, demonstrating a significant discrepancy with observations at low metallicity. We model the abundance changes during extra mixing as a thermohaline process and determine that the usual diffusive form of this mechanism cannot simultaneously reproduce both the carbon and lithium observations. Hubble Space Telescope photometry provides turnoff and bump magnitudes in a large number of globular clusters and offers the opportunity to better test stellar modelling as function of metallicity. We directly compare the predicted main-sequence turn-off and bump magnitudes as well as the distance-independent parameter ∆M V MSTO bump . We require 15 Gyr isochrones to match the main-sequence turn-off magnitude in some clusters and cannot match the bump in low-metallicity systems. Changes to the distance modulus, metallicity scale and bolometric corrections may impact on the direct comparisons but ∆M V MSTO bump , which is also underestimated from the models, can only be improved through changes to the input physics. Overshooting at the base of the convective envelope with an efficiency that is metallicity dependent is required to reproduce the empirically determined value of ∆M V MSTO bump .

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Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)★

Cited by 143 publications

References 132 publications

A Spectroscopic Analysis of the Galactic Globular Cluster NGC 6273 (M19)

A Spectroscopic Analysis of the Galactic Globular Cluster NGC 6273 (M19)

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

Diagnostics of stellar modelling from spectroscopy and photometry of globular clusters

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