Metallicity Variations in the Type II Globular Cluster NGC 6934*

Marino, A. F.; Yong, David; Milone, A. P.; Piotto, G.; Lundquist, M.; Bedin, L. R.; Chené, A. N.; Costa, G. S. Da; Asplund, Martin; Jerjen, Helmut

doi:10.3847/1538-4357/aabdea

Cited by 42 publications

(63 citation statements)

References 63 publications

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“…ωCen, NGC 6934 Norris & Da Costa 1995;Marino et al 2018), the relatively low star-to-star metallicity dispersion as shown in Fig. 5 is consistent with the conclusions of Carretta et al (2009a), claiming that most of the clusters can be considered mono-metallic regarding the Fe abundance.…”

Section: Metallicitysupporting

confidence: 84%

Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code

Masseron

García–Hernández

Mészáros

et al. 2019

A&A

158

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Aims. We aim at providing abundances of a large set of light and neutron-capture elements homogeneously analyzed and covering a wide range of metallicity to constrain globular cluster (GC) formation and evolution models. Methods. We analyze a large sample of 885 GCs giants from the APOGEE survey. We used the Cannon results to separate the red giant branch and the asymptotic giant branch stars, not only allowing for a refinement of surface gravity from isochrones, but also providing an independent H-band spectroscopic method to distinguish stellar evolutionary status in clusters. We then use the BACCHUS code to derive metallicity, microturbulence, macroturbulence and many light-element abundances as well as the neutron-capture elements Nd and Ce for the first time from the APOGEE GCs data. Results. Our independent analysis helped us to diagnose issues regarding the standard analysis of the APOGEE DR14 for lowmetallicity GC stars. Furthermore, while we confirm most of the known correlations and anti-correlation trends (Na-O, Mg-Al, C-N), we discover that some stars within our most metal-poor clusters show an extreme Mg depletion and some Si enhancement but at the same time show some relative Al depletion, displaying a turnover in the Mg-Al diagram. These stars suggest that Al has been partially depleted in their progenitors by very hot proton-capture nucleosynthetic processes. Furthermore, we attempted to quantitatively correlate the spread of Al abundances with the global properties of GCs. We find an anti-correlation of the Al spread against clusters metallicity and luminosity, but the data do not allow to find clear evidence of a dependence of N against metallicity in the more metal-poor clusters. Conclusions. Large and homogeneously analyzed samples from on-going spectroscopic surveys unveil unseen chemical details for many clusters, including a turnover in the Mg-Al anti-correlation, thus yielding new constrains for GCs formation/evolution models.

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Section: Metallicitysupporting

confidence: 84%

Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code

Masseron

García–Hernández

Mészáros

et al. 2019

A&A

158

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“…The first GC where this spread has been observed is ωCen (Norris & Da Costa 1995), a cluster strongly suspected to be the remnant nucleus of a disrupted dwarf galaxy (Freeman 1993;Dinescu et al 1999;Hughes & Wallerstein 2000;Bekki & Freeman 2003;Böker 2008). While the iron spread found in some clusters (M22, Hesser et al 1977;Marino et al 2009Marino et al , 2011Marino et al , 2012Marino et al , 2013Lee 2015) is still controversial (Mucciarelli et al 2015;Lee 2016), the latest works confirm previous finding and the number of clusters where this peculiarity is detected is increasing with time (Marino et al 2018). Recent analysis added M22 (Hesser et al 1977;Marino et al 2009Marino et al , 2011Marino et al , 2012Marino et al , 2013Lee 2015), M2 Lardo et al 2013;Milone et al 2015), M54 (Sarajedini & Layden 1995;Bellazzini et al 2008;Carretta et al 2010a), NGC 1851 Carretta et al 2010c;Yong & Grundahl 2008;Carretta et al 2011), NGC 5286 (Nataf et al 2013;Marino et al 2015), NGC 5824 (Sa-viane et al 2012;Da Costa et al 2014), Terzan 5 (Ferraro et al 2009;Massari et al 2014), M19 (Johnson et al 2015) and NGC 6934 (Marino et al 2018) to the list of clusters with iron spreads.…”

Section: Introductionsupporting

confidence: 61%

“…In this paper we illustrated how massive primordial thick disc GCs can merge or have mass exchanges, a fact that could explain the metallicity spreads observed in a small, but growing (Marino et al 2018), fraction of the massive Galactic GCs. The main results achieved by studying of the long term-evolution of interacting clusters can be summarised as follows:…”

Section: Discussionmentioning

confidence: 97%

Mergers, tidal interactions, and mass exchange in a population of disc globular clusters

Mastrobuono-Battisti

Khoperskov

Matteo

et al. 2019

A&A

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Globular clusters (GCs), the oldest stellar systems observed in the Milky Way, have for long been considered single stellar populations. As such, they provided an ideal laboratory to understand stellar dynamics and primordial star formation processes. However, during the last two decades, observations unveiled their real, complex nature. Beside their pristine stars, GCs host one or more helium enriched and possibly younger stellar populations whose formation mechanism is still unknown. Even more puzzling is the existence of GCs showing star by star iron spreads. Using detailed N-body simulations we explore the hypothesis that these anomalies in metallicity could be the result of mutual stripping and mergers between a primordial population of disc GCs. In the first paper of this series we proved, both with analytical arguments and short-term N-body simulations, that disc GCs have larger fly-by and close encounter rates with respect to halo clusters. These interactions lead to mass exchange and even mergers that form new GCs, possibly showing metallicity spreads. Here, by means of long-term direct N-body simulations, we provide predictions on the dynamical properties of GCs that underwent these processes. The comparison of our predictions with available and future observational data could provide insights on the origin of GCs and on the Milky Way build-up history as a whole.

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“…The sample of all Type II GCs comprises NGC 362, NGC 1261, NGC 1851, NGC 6715 (M 54), NGC 6934, NGC 7078 (M 15), NGC 7089 (M 2) and Terzan 5 (e.g. Marino et al 2009Marino et al , 2015Marino et al , 2018bDa Costa et al 2009;Yong & Grundahl 2008;Yong et al 2014Yong et al , 2016Carretta et al 2010;Johnson et al 2015Johnson et al , 2017Nardiello et al 2018;Ferraro et al 2009;Massari et al 2014).…”

Section: Type II Gcs In the Integral Of Motion Spacementioning

confidence: 99%

Multiple populations in globular clusters and their parent galaxies

Milone

Marino²,

Costa

et al. 2019

Monthly Notices of the Royal Astronomical Society

Self Cite

102

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The 'chromosome map' diagram (ChM) proved a successful tool to identify and characterize multiple populations (MPs) in 59 Galactic Globular Clusters (GCs). Here, we construct ChMs for 11 GCs of both Magellanic Clouds (MCs) and with different ages to compare MPs in Galactic and extra-Galactic environments, and explore whether this phenomenon is universal through 'place' and 'time'. MPs are detected in five clusters. The fractions of 1G stars, ranging from ∼50% to >80%, are significantly higher than those observed in Galactic GCs with similar present-day masses. By considering both Galactic and MC clusters, the fraction of 1G stars exhibits: (i) a strong anti-correlation with the present-day mass, and (ii) with the present-day mass of 2G stars; (iii) a mild anti-correlation with 1G present-day mass. All Galactic clusters without MPs have initial masses smaller than ∼ 1.5 · 10 5 M but a mass threshold governing the occurrence of MPs seems challenged by massive simple-population MC GCs; (iv) Milky Way clusters with large perigalactic distances typically host larger fractions of 1G stars, but the difference disappears when we use initial cluster masses. These facts are consistent with a scenario where the stars lost by GCs mostly belong to the 1G. By exploiting recent work based on Gaia, half of the known Type II GCs appear clustered in a distinct region of the integral of motions space, thus suggesting a common progenitor galaxy. Except for these Type II GCs, we do not find any significant difference in the MPs between clusters associated with different progenitors.

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Metallicity Variations in the Type II Globular Cluster NGC 6934*

Cited by 42 publications

References 63 publications

Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code

Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code

Mergers, tidal interactions, and mass exchange in a population of disc globular clusters

Multiple populations in globular clusters and their parent galaxies

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