Theoretical isochrones for globular clusters with predicted BVRI and Stromgren photometry

VandenBerg, Don A.; Bell, R. A.

doi:10.1086/191052

Cited by 186 publications

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“…Similarly, Alcaino et al (1990) derive an age of 15 ±3 Gyr to their CMD using VandenBerg and Bell (1985) Alternatively, NGC 2298 and M92 have been found to be coeval to within 0.5 Gyr by VandenBerg et al (1990). The age of M92 has been found to be 16-17 Gyr by Stetson and Harris (1988) Harris data and appropriate isochrones should then be increased by -1 Gyr, to 17-18 Gyr, a value somewhat higher than the above estimation.…”

Section: Age Of Ngc 2298mentioning

confidence: 85%

Abundance analysis of three red giants in the metal-poor globular cluster NGC 2298

McWilliam

Geisler

Rich

1992

PASP

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ABSTRACT. We have obtained high-resolution, high-signal-to-noise-ratio echelle CCD spectra of three red giants in the metal-poor globular cluster NGC 2298. (1991). The a elements Mg, Si, and Ca are enhanced more than oxygen, with an average of [a/Fe] = H-0.47, suggesting an oxygen depletion as might be expected from proton burning by the CNO tri-cycle. A1 is strongly overabundant in all three stars relative to typical values found in field halo giants of similar metallicity. This A1 overabundance could be due to proton burning of the envelope material by the Mg-Al cycle. The apparent dispersion in A1 abundance would suggest that the A1 overabundance is due to self-enrichment by the individual stars, rather than Al-rich primordial gas, but this conclusion requires verification. Based on our metallicity and composition we apply corrections to the estimated age of NGC 2298 found by previous studies, giving an age range of 14-18 Gyr. Our O and a-element abundances for NGC 2298, combined with those of other recent investigations of the most metal-poor globular clusters, indicate substantially lower values than measured by Abia and Rebolo (1989) or assumed O enhancements in the isochrones of McClure et al. (1987), leading to somewhat larger ages for these most ancient Galactic systems.

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Section: Age Of Ngc 2298mentioning

confidence: 85%

Abundance analysis of three red giants in the metal-poor globular cluster NGC 2298

McWilliam

Geisler

Rich

1992

PASP

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“…There are many calibrations between the normalised ultraviolet excess (δ U−B ) 0.6 and the metal abundance [Fe/H] for the last system which deviate from each other considerably. Figure 15 of Buser & Kurucz (1992) compares these calibrations based on empirical data (Cameron 1985, Carney 1979 or theoretical models (Buser & Kurucz 1978, 1985, and Vandenberg & Bell 1985. The reason for these differences originates from the UBV data as well as from the atmospheric parameters.…”

Section: Introductionmentioning

confidence: 99%

New Metallicity Calibration Down to [Fe/H] = −2.75 dex

Karaali

Bilir

Karataş

et al. 2003

Publ. – Astron. Soc. Aust

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Abstract:We have taken 88 dwarfs, covering the colour-index interval 0.37 ≤ (B−V) 0 ≤ 1.07 mag, with metallicities −2.70 ≤ [Fe/H] ≤+ 0.26 dex, from three different sources for new metallicity calibration. The catalogue of Cayrel de Strobel et al. (2001), which includes 65% of the stars in our sample, supplies detailed information on abundances for stars with determination based on high-resolution spectroscopy. In constructing the new calibration we have used as 'corner stones' 77 stars which supply at least one of the following conditions: (i) the parallax is larger than 10 mas (distance relative to the Sun less than 100 pc) and the galactic latitude is absolutely higher than 30 • ; (ii) the parallax is rather large, if the galactic latitude is absolutely low and vice versa. Contrary to previous investigations, a third-degree polynomial is fitted for the new calibration: [Fe/H] = 0.10 − 2.76δ − 24.04δ 2 + 30.00δ 3 . The coefficients were evaluated by the least-squares method, without regard to the metallicity of Hyades. However, the constant term is in the range of metallicity determined for this cluster, i.e. 0.08 ≤ [Fe/H] ≤ 0.11 dex. The mean deviation and the mean error in our work are equal to those of Carney (1979)

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“…Although the very powerful method of model isochrone fitting to observed CMDs has been used for decades to age-date these large sample of stars (e.g. Vandenberg and Bell, 1985), it is still limited by the uncertainties inherent to stellar evolutionary models, but also to the error on apparent distance modulus, on reddening, and on the relations between colors and effective temperature, bolometric correction scale, etc (e.g. Cassisi, 2014;Casagrande and VandenBerg, 2014; Lebreton et al, 2014, and references therein).…”

Section: Importance Of Globular Clusters For Cosmology and For Galactmentioning

confidence: 99%

Multiple Stellar Populations and Their Evolution in Globular Clusters: A Nucleosynthesis Perspective

Charbonnel

2016

EAS Publications Series

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Abstract. This paper presents a review of the characteristics of the multiple stellar populations observed in globular clusters, and of their possible origin. The current theoretical issues and the many open questions are discussed. Importance of globular clusters for cosmology and for galactic physicsGlobular clusters (GC) are magnificent astronomical objects that provide insight to a broad variety of astronomical and cosmological questions. These compact systems that contain between several hundreds of thousands and a million stars are among the oldest structures in the Universe. They are unique relics, witnesses, and clocks of the formation, assembly, dynamics, and evolution of galaxies and of their substructures, from the early to the present-day Universe. They play a key role in hierarchical cosmology, and potentially also in the reionization of the Universe, and they provide fundamental benchmarks for stellar evolution theory. However, their formation, evolution, and survival in a galactic and cosmological context are far from being understood.Determining the age of the oldest GCs through isochrone fitting of their observed color-magnitude diagram (CMD) was crucial for cosmology until the beginning of the 21 st century, as it provided the best lower limit to the age of the Universe (e.g. Carney, 2001, and references therein). Meanwhile, a robust determination of the age of the Universe was made possible thanks to precise observations of the cosmic microwave background (CMB) by the Wilkinson Microwave Anisotropy Probe and Planck satellites. The age of the universe is now estimated (EES 2015) to be ∼ 13.8 according to flat Λ CMD model that accurately reproduces the observed temperature of the power spectrum of the CMB (Planck Collaboration, Ade et al., 2015). This agrees with the current estimate of the age of the oldest Galactic GCs that were among the first baryonic structures to form in galaxies about 13 Gyr ago (e.g. VandenBerg et al., 2013).Determining the absolute and relative ages of GCs is still very important today, for various reasons. This helps constraining the models of the formation of these systems in the more general context of the formation and early evolution of galaxies (e.g. Fall and Rees, 1985;Harris, 1991;Forbes et al., 1997; van den Bergh, 2011). Different scenarios make indeed different predictions for the age of the oldest GCs, as well as for the dispersion in age at a given metallicity (or rather [Fe/H]) and/or galactocentric distance. There is a wealth of literature on these questions, and we quote here only a few illustrative examples. Brodie and Strader (2006) argue that the most metal-poor GCs, which inhabit the haloes of spiral galaxies, were created in low-mass dark matter haloes at redshift higher than 10 (see also Bromm and Clarke 2002), and that metal-rich GCs formed during later mergers of gas-rich structures that build up the parent galaxies. On the other hand, cosmological N-body simulations and semi-analytic models of galaxy and GC formation accounting for the impo...

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Theoretical isochrones for globular clusters with predicted BVRI and Stromgren photometry

Cited by 186 publications

References 0 publications

Abundance analysis of three red giants in the metal-poor globular cluster NGC 2298

Abundance analysis of three red giants in the metal-poor globular cluster NGC 2298

New Metallicity Calibration Down to [Fe/H] = −2.75 dex

Multiple Stellar Populations and Their Evolution in Globular Clusters: A Nucleosynthesis Perspective

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