M. E. Sharina, V. V. Shimansky, E. Davoust
NGC 2419 is the most distant massive globular cluster in the outer Galactic halo. It is unusual also due to the chemical peculiarities found in its red giants in recent years. We study the stellar population of this unusual object using spectra obtained at the 1.93-m telescope of the Haute-Provence Observatory. At variance with commonly used methods of high-resolution spectroscopy applicable only to bright stars, we employ spectroscopic information on the integrated light of the cluster. We carry out population synthesis modeling of medium-resolution spectra using synthetic stellar atmosphere models based on a theoretical isochrone corresponding accurately to the observed color-magnitude diagram. We study the influence of non-Local Thermodynamic Equilibrium for some chemical elements on our results. The derived age (12.6 Gyr), [Fe/H]=-2.25 dex, helium content Y=0.25, and abundances of 12 other chemical elements are in a good qualitative agreement with published high-resolution spectroscopy estimates for red giant members in the cluster. On the other hand, the derived element abundance, [alpha/Fe]=0.13 dex (the mean of [O/Fe], [Mg/Fe] and [Ca/Fe]), differs from the published one ([alpha/Fe] =0.4). We suggest that studies of the integrated light in NGC2419 using high-resolution spectrographs in different wavelength regions will help to understand the nature of these chemical anomalies.
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http://arxiv.org/abs/1211.3035
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