Chemical Abundances of Red Giant Stars in the Globular Cluster M107 (NGC 6171)

O’Connell, Julia; Johnson, Christian I.; Pilachowski, Catherine A.; Burks, G. S.

doi:10.1086/662138

Cited by 20 publications

(10 citation statements)

References 53 publications

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“…However, unlike low metallicity globular clusters, NGC 6553 does not exhibit a strong Na-Al correlation. This is in agreement with the observed trend that the Na-Al correlation is more mild and [Al/Fe] dispersions smaller in metal-rich as opposed to metal-poor globular clusters (e.g., Carretta et al 2009;O'Connell et al 2011;Cordero et al 2014). Unfortunately, the 6300 Å telluric oxygen emission feature combined with NGC 6553's relatively low radial velocity prohibited us from obtaining an [O/Fe] abundance for more than one star in NGC 6553.…”

Section: The Light Odd-z Elements Sodium and Aluminumsupporting

confidence: 89%

LIGHT, ALPHA, AND Fe-PEAK ELEMENT ABUNDANCES IN THE GALACTIC BULGE

Johnson

Rich

Kobayashi

et al. 2014

The Astronomical Journal

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148

273

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We present radial velocities and chemical abundances of O, Na, Mg, Al, Si, Ca, Cr, Fe, Co, Ni, and Cu for a sample of 156 red giant branch stars in two Galactic bulge fields centered near (l,b)=(+5.25,-3.02) and (0,-12). The (+5.25,-3.02) field also includes observations of the bulge globular cluster NGC 6553. The results are based on high resolution (R∼20,000), high signal-to-noise (S/N 70) FLAMES-GIRAFFE spectra obtained through the ESO archive. However, we only selected a subset of the original observations that included spectra with both high S/N and that did not show strong TiO absorption bands. The present work extends previous analyses of this data set beyond Fe and the α-elements Mg, Si, Ca, and Ti. While we find reasonable agreement with past work, the data presented here indicate that the bulge may exhibit a different chemical composition than the local thick disk, especially at [Fe/H] -0.5. In particular, the bulge [α/Fe] ratios may remain enhanced to a slightly higher [Fe/H] than the thick disk and the Fe-peak elements Co, Ni, and Cu appear enhanced compared to the disk. There is also some evidence that the [Na/Fe] (but not [Al/Fe]) trends between the bulge and local disk may be different at low and high metallicity. We also find that the velocity dispersion decreases as a function of increasing [Fe/H] for both fields, and do not detect any significant cold, high velocity population. A comparison with chemical enrichment models indicates that a significant fraction of hypernovae are required to explain the bulge abundance trends, and that initial mass functions that are steep, top-heavy (and do not include strong outflow), or truncated to avoid including contributions from stars >40 M ⊙ are ruled out, in particular because of disagreement with the Fe-peak abundance data. For most elements, the NGC 6553 stars exhibit nearly identical abundance trends to comparable metallicity bulge field stars. However, the star-to-star scatter and mean [Na/Fe] ratios appear higher in the cluster, perhaps indicating additional self-enrichment.

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Section: The Light Odd-z Elements Sodium and Aluminumsupporting

confidence: 89%

LIGHT, ALPHA, AND Fe-PEAK ELEMENT ABUNDANCES IN THE GALACTIC BULGE

Johnson

Rich

Kobayashi

et al. 2014

The Astronomical Journal

Self Cite

148

273

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“…Figure 11 indicates that there may be a pattern of decreasing [Na/Fe] dispersion for the more metal-rich populations of NGC 6273, ω Cen, and possibly NGC 5286. We note that a decrease in [Na/Fe] dispersion with increasing [Fe/H] would fit a global trend observed in monometallic globular clusters as well (e.g., Carretta et al 2009b, their both the maximum [Al/Fe] abundance and dispersion for the more metal-rich populations is clearly seen in both NGC 6273 and ω Cen (Figure 12), and also matches trends observed in monometallic clusters (e.g., Carretta et al 2009b;O'Connell et al 2011;Cordero et al 2014Cordero et al , 2015. The prominent bimodal [Al/Fe] distribution of NGC 6273 is also clearly seen in ω Cen, M54+Sagittarius, and possibly M2.…”

Section: Comparison With Other "Iron-complex"supporting

confidence: 81%

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

Johnson

Rich

Pilachowski

et al. 2015

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129

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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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“…In particular, according to both observations (see e.g. Carretta et al 2009) and theoretical predictions (Ventura et al 2014), the Al production in GCs depends on two main parameters: (i) metallicity, since a high metallicity causes lower Al-yields from polluters 6 (Ventura & D'Antona 2009;Karakas 2010;O'Connell et al 2011) and (ii) cluster mass, since (under the hypothesis of the same initial mass function) a more massive cluster would have more polluters and would retain more polluted gas within its potential well. However, several exceptions to these trends exist, such as 47 Tucanae (which shows a small Al spread despite being quite massive, see Cordero et al 2014) or M71 (which is an outlier in the Carretta relation, see Carretta et al 2009;Cordero et al 2015).…”

Section: Discussionmentioning

confidence: 95%

The chemical composition of the low-mass Galactic globular cluster NGC 6362★

Massari

Mucciarelli

Dalessandro

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present chemical abundances for 17 elements in a sample of 11 red giant branch stars in NGC 6362 from UVES spectra. NGC 6362 is one of the least massive globulars where multiple populations have been detected, yet its detailed chemical composition has not been investigated so far. NGC 6362 turns out to be a metal-intermediate ([Fe/H]=-1.07±0.01 dex) cluster, with its α-and Fe-peak elements content compatible with that observed in clusters with similar metallicity. It also displays an enhancement in its s-process element abundances. Among the light elements involved in the multiple populations phenomenon, only [Na/Fe] shows star-to-star variations, while [Al/Fe] and [Mg/Fe] do not show any evidence for abundance spreads. A differential comparison with M4, a globular cluster with similar mass and metallicity, reveals that the two clusters share the same chemical composition. This finding suggests that NGC 6362 is indeed a regular cluster, formed from gas that has experienced the same chemical enrichment of other clusters with similar metallicity.

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Chemical Abundances of Red Giant Stars in the Globular Cluster M107 (NGC 6171)

Cited by 20 publications

References 53 publications

LIGHT, ALPHA, AND Fe-PEAK ELEMENT ABUNDANCES IN THE GALACTIC BULGE

LIGHT, ALPHA, AND Fe-PEAK ELEMENT ABUNDANCES IN THE GALACTIC BULGE

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

The chemical composition of the low-mass Galactic globular cluster NGC 6362★

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