Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Population Synthesis in the Blue II. The Spectroscopic Age of 47 Tucanae   We develop a new set of models for intermediate-metallicity single stellar
populations in the blue/optical region and use those models to determine the
spectroscopic age of 47 Tuc. The models are based on a moderately
high-resolution (1.8 A FWHM) empirical spectral library, state-of-the-art
theoretical isochrones from M. Salaris and the most recent set from the Padova
group, and new semi-empirical calibrations between fundamental stellar
parameters and observables. We highlight the importance of correctly modeling
the luminosity function (LF) of the cluster at the level of the giant branch,
in order to achieve a good reproduction of the integrated spectrum; agreement
between the spectroscopic age and the age based on the cluster's
color-magnitude diagram (CMD) is achieved only if the observed LF is used
rather than the theoretical ones, which either do not include AGB stars
(Salaris) or underpredict the total number counts of bright giants in the
cluster by a factor of two(Padova). After all corrections are made, the CMD and
the spectroscopic ages (from Hgamma and Hbeta) are in close agreement: 11--12
Gyrs for Salaris isochrones and about 13 Gyrs for Padova. The difference
between the model ages is due to the inclusion of atomic diffusion in the
Salaris models. Previously older spectroscopic ages were due to the
underestimate of the number of red giants and/or the use of isochrones that
neglected the effects of He-diffusion and alpha-enhancement. A similar
underestimate in the bright giant LF, if it exists in current super-solar
metallicity models, would cause spectroscopic ages of elliptical galaxies
inferred from such models to be too high by approximately 30%.

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The categories of this paper are: solv-int
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The categories of this paper are: chao-dyn
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The categories of this paper are: cmp-lg
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The categories of this paper are: plasm-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: nlin
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The categories of this paper are: supr-con
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The categories of this paper are: funct-an
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The categories of this paper are: hep-th
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The categories of this paper are: cond-mat
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-th