A Chemical Composition Survey of the Iron-complex Globular Cluster NGC 6273 (M19)*

Johnson, Christian I.; Caldwell, Nelson; Rich, R. Michael; Mateo, Mario; Bailey, John I.; Clarkson, W. I.; Olszewski, Edward W.; Walker, Matthew G.

doi:10.3847/1538-4357/836/2/168

Cited by 52 publications

(57 citation statements)

References 210 publications

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“…Our previous studies, however, found a significant CN-CH positive correlation, instead of an anticorrelation, among RGB stars in M22 and NGC 6273 Lim et al 2015). Interestingly, both GCs are known to host multiple stellar populations with different heavy element abundances (see also Marino et al 2011;Johnson et al 2017). Since NGC 5286 is also one of the GCs showing spreads in the abundances of heavy elements, we would expect a similar positive correlation between CN and CH indices.…”

Section: The Cn-ch Positive Correlation In Globular Clusters With Heamentioning

confidence: 86%

The CN–CH Positive Correlation in the Globular Cluster NGC 5286

Lim¹,

Hong²,

Lee³

2017

ApJ

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We performed low-resolution spectroscopy for the red giant stars in the Galactic globular cluster (GC) NGC 5286, which is known to show intrinsic heavy element abundance variations. We found that the observed stars in this GC are clearly divided into three subpopulations by CN index (CN-weak, CN-intermediate, and CN-strong). The CN-strong stars are also enhanced in the calcium HK (7.4σ) and CH (5.1σ) indices, while the CN-intermediate stars show no significant difference in the strength of HK index with CN-weak stars. From the comparison with high-resolution spectroscopic data, we found that the CN-and HK -strong stars are also enhanced in the abundances of Fe and s-process elements. It appears, therefore, that these stars are later generation stars affected by some supernovae enrichment in addition to the asymptotic giant branch ejecta. In addition, unlike normal GCs, sample stars in NGC 5286 show the CN-CH positive correlation, strengthening our previous suggestion that this positive correlation is only discovered in GCs with heavy element abundance variations such as M22 and NGC 6273.

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Section: The Cn-ch Positive Correlation In Globular Clusters With Heamentioning

confidence: 86%

The CN–CH Positive Correlation in the Globular Cluster NGC 5286

Lim¹,

Hong²,

Lee³

2017

ApJ

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“…ChMs have also revealed the presence of two classes of clusters, namely Type I and Type II GCs, with the latter constituting ∼17% of the objects and displaying a more complex chemical pattern, including variations in Fe and heavy elements (e.g. Marino et al 2009Marino et al , 2015Yong & Grundahl 2008;Yong et al 2014;Johnson et al 2015Johnson et al , 2017Da Costa et al 2009). According to some scenarios, GCs have experienced multiple bursts of star formation where 2G stars formed from material polluted by more massive 1G stars (e.g.…”

Section: Introductionmentioning

confidence: 99%

Multiple populations in globular clusters and their parent galaxies

Milone

Marino²,

Costa

et al. 2019

Monthly Notices of the Royal Astronomical Society

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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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“…As noted by numerous previous authors (e.g., Armandroff & Da Costa 1991;Olszewski et al 1991;Idiart et al 1997;Rutledge et al 1997;Battaglia et al 2008), the near-infrared CaT lines are reliable tracers of a star's metallicity and are relatively insensitive to age and [Ca/Fe] abundance variations (e.g., Cole et al 2004;Carrera et al 2007;Da Costa 2016b). Following the methods outlined in Yong et al (2016) and Johnson et al (2017a), we employed the calibration described in Mauro et al (2014) to convert the measured CaT EWs into [Fe/H] abundances. A key advantage of the Mauro et al (2014) CaT-[Fe/H] calibration is that a star's luminosity parameter is defined as the difference between its K S -band magnitude and that of the HB.…”

Section: Calcium Triplet [Fe/h] Determinationsmentioning

confidence: 99%

“…These "iron-complex" clusters exhibit significant [Fe/H] dispersions and share a common trait that metallicity and s-process enhancements are strongly correlated (e.g., Norris & Da Costa 1995;Smith et al 2000;Johnson & Pilachowski 2010;Marino et al 2011aMarino et al , 2011bYong et al 2014;Johnson et al 2015bJohnson et al , 2017aMarino et al 2015;Da Costa 2016a). 9 Since second-peak s-process elements are thought to be produced during the late-stage evolution of low-and intermediate-mass AGB stars (e.g., Busso et al 1999), the correlation between [Ba, La/Fe] and [Fe/H] is consistent with the idea that ironcomplex clusters experienced prolonged star formation and chemical enrichment compared to monometallic systems.…”

Section: Introductionmentioning

confidence: 99%

Exploring the Chemical Composition and Double Horizontal Branch of the Bulge Globular Cluster NGC 6569

Johnson

Rich

Caldwell

et al. 2018

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Photometric and spectroscopic analyses have shown that the Galactic bulge cluster Terzan 5 hosts several populations with different metallicities and ages that manifest as a double red horizontal branch (HB). A recent investigation of the massive bulge cluster NGC 6569 revealed a similar, though less extended, HB luminosity split, but little is known about the cluster's detailed chemical composition. Therefore, we have used high-resolution spectra from the Magellan-M2FS and VLT-FLAMES spectrographs to investigate the chemical compositions and radial velocity distributions of red giant branch and HB stars in NGC 6569. We found the cluster to have a mean heliocentric radial velocity of −48.8 km s 11 dex indicates significant pollution with r-process material. We confirm that both HBs contain cluster members, but metallicity and lightelement variations are largely ruled out as sources for the luminosity difference. However, He mass fraction differences as small as ΔY∼0.02 cannot be ruled out and may be sufficient to reproduce the double HB.

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A Chemical Composition Survey of the Iron-complex Globular Cluster NGC 6273 (M19)*

Cited by 52 publications

References 210 publications

The CN–CH Positive Correlation in the Globular Cluster NGC 5286

The CN–CH Positive Correlation in the Globular Cluster NGC 5286

Multiple populations in globular clusters and their parent galaxies

Exploring the Chemical Composition and Double Horizontal Branch of the Bulge Globular Cluster NGC 6569

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