The Giant Branch of omega Centauri. V. The Calcium Abundance Distribution

Norris, John E.; Freeman, K. C.; Mighell, Kenneth J.

doi:10.1086/177145

Cited by 197 publications

(294 citation statements)

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“…This definitely removes the possibility raised in B04 that the bMS represents a super-metal-poor population. The [Fe/H] of the rMS is consistent with the peak of the abundance distribution of red giants in ω Cen (Suntzeff & Kraft 1996;Norris et al 1996), while the bMS corresponds roughly to the second peak in the distribution obtained by those authors. Also, the relative number of stars in the two sequences is consistent with the relative numbers in the RGB.…”

Section: Globular Clusters With Flamessupporting

confidence: 87%

Observations of globular clusters with FLAMES

Gratton¹,

Bragaglia

Carretta

et al. 2005

Proc. IAU

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Abstract. We present preliminary results of a few observing programs conducted with the FLAMES fiber facility at VLT2 ESO telescope. These programs show the large potentiality of FLAMES for investigations of globular clusters. The programs described here concern the derivation of precise reddening and metallicity for globular clusters, and the derivation of abundances for stars on the main sequence of ω Cen. Reddenings with errors of ∆E(B − V ) = 0.005 mag and metallicities with errors of ±0.02 dex (in a scale defined by local subdwarfs) can be obtained in very short observing time. Our results for ω Cen show that the blue main sequence is more metal-rich than the red-main sequence: this requires a large He-content for the blue main sequence.

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Section: Globular Clusters With Flamessupporting

confidence: 87%

Observations of globular clusters with FLAMES

Gratton¹,

Bragaglia

Carretta

et al. 2005

Proc. IAU

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“…The MDF shows a bimodal structure similar to that observed in ω Cen (e.g. Norris et al 1996) Given the distictive role of the SN Ia pollution, the [Fe/H] content of this system is not simply proportional to the metal content and a large spread in the age-metallicity relation is always present (see Fig. 3).…”

Section: ω Censupporting

confidence: 59%

About the Chemical Evolution of dSphs (and the peculiar Globular Cluster ω Cen)

Marcolini

D’Ercole

2008

Proc. IAU

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Abstract.We present three dimensional hydrodynamical simulations aimed at studying the dynamical and chemical evolution of the interstellar medium (ISM) in isolated dwarf spheroidal galaxies (dSphs). This evolution is driven by the explosion of Type II and Type Ia supernovae, whose different contribution on both the dynamics and chemical enrichment is taken into account. Radiative losses are effective in radiating away the huge amount of energy released by SNe explosions, and the dSph is able to retain most of the gas allowing a long period ( 2 − 3 Gyr) of star formation, as usually observed in this kind of galaxies. We are able to reproduce the stellar metallicity distribution function (MDF) as well as the peculiar chemical properties of strongly O-depleted stars observed in several dSphs. The model also naturally predicts two different stellar populations, with an anti-correlation between [Fe/H] and velocity dispersion, similarly to what observed in the Sculptor and Fornax dSphs. These results derive from the inhomogeneous pollution of the SNe Ia, a distinctive characteristic of our model. We also applied the model to the peculiar globular cluster (GC) ω Cen in the hypothesis that it is the remnant of a formerly larger stellar system, possibly a dSph.

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“…From the pioneering studies in the 60 s to the latest high-quality data and models, more and more details of its multiple stellar populations have come to light, but the picture did not become as clear as expected. Excellent photometries and astrometric catalogues have recently been produced by both groundbased (such as Lee et al 1999;Pancino et al 2000;van Leeuwen et al 2000;Hilker & Richtler 2000;Hughes & Wallerstein 2000;Sollima et al 2005a;Calamida et al 2009;Bellini et al 2009) and space telescopes (e.g., Ferraro et al 2004;Bedin et al 2004;Bellini et al 2010), complemented by high-quality spectroscopic abundance studies both at high (e.g., Norris & Da Costa 1995;Smith et al 2000;Cunha et al 2002;Pancino 2003;Johnson et al 2008Johnson et al , 2009Johnson & Pilachowski 2010;Marino et al 2010) and low (Norris et al 1996;Suntzeff & Kraft 1996;Sollima et al 2005b;Stanford et al 2006;Villanova et al 2007) resolution. Nevertheless, several puzzles still await solutions.…”

Section: Introductionmentioning

confidence: 99%

The subgiant branch ofω Centauri seen through high-resolution spectroscopy

Pancino¹,

Mucciarelli²,

Sbordone³

et al. 2011

A&A

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We analysed high-resolution UVES spectra of six stars belonging to the subgiant branch of ω Centauri, and derived abundance ratios of 19 chemical elements (namely Al, Ba, C, Ca, Co, Cr, Cu, Fe, La, Mg, Mn, N, Na, Ni, Sc, Si, Sr, Ti, and Y). A comparison with previous abundance determinations for red giants provided remarkable agreement and allowed us to identify the sub-populations to which our targets belong. We found that three targets belong to a low-metallicity population at [Fe/H] -2.0 dex, [α/Fe] +0.4 dex and [s/Fe] 0 dex. Stars with similar characteristics were found in small amounts by past surveys of red giants. We discuss the possibility that they belong to a separate sub-population that we name VMP (very metal-poor, at most 5% of the total cluster population), which -in the self-enrichment hypothesis -is the best-candidate first stellar generation in ω Cen. Two of the remaining targets belong to the dominant metal-poor population (MP) at [Fe/H] -1.7 dex, and the last one to the metal-intermediate (MInt) one at [Fe/H] -1.2 dex. The existence of the newly defined VMP population could help to understand some puzzling results based on low-resolution spectroscopy for age differences determinations, because the metallicity resolution of these studies was probably not enough to detect the VMP population. The VMP could also correspond to some of the additional substructures of the subgiant-branch region found in the latest HST photometry. After trying to correlate chemical abundances with substructures in the subgiant branch of ω Cen, we found that the age difference between the VMP and MP populations should be small (0 ± 2 Gyr), while the difference between the MP and MInt populations could be slightly larger (2 ± 2 Gyr).

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The Giant Branch of omega Centauri. V. The Calcium Abundance Distribution

Cited by 197 publications

References 0 publications

Observations of globular clusters with FLAMES

Observations of globular clusters with FLAMES

About the Chemical Evolution of dSphs (and the peculiar Globular Cluster ω Cen)

The subgiant branch ofω Centauri seen through high-resolution spectroscopy

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