Analysis of integrated-light spectra of Galactic globular clusters
  We present the results of determination of the age, helium mass fraction (Y)
in terms of the used stellar evolutionary models, metallicity ([Fe/H]), and
abundances of the elements C, O, Na, Mg, Ca, Ti, Cr and Mn for 26 globular
clusters of the Galaxy. In this work, we apply a method developed by us that
employs medium-resolution integrated-light spectra of globular clusters and
models of stellar atmospheres and it is supplemented in this paper by the
automatic calculation of microturbulence velocities of stars in the studied
objects. Based on the data obtained for 26 objects, as well as on the results
of our previous studies, it is shown that the abundances of chemical elements,
that we measured, with the exception of carbon, are consistent with the
literature estimates from the analysis of integrated-light spectra of clusters
and from high-resolution spectroscopic observations of their brightest stars.
Our estimates of [C/Fe] are consistent with the literature values obtained from
the integrated-light spectra of clusters. We interpret the systematic
difference between the derived [C/Fe] for globular clusters and the literature
[C/Fe] values for the brightest stars of the clusters as a change of the
chemical composition in the atmospheres of stars during their evolution. The
estimated absolute ages and average Y for the clusters are in a reasonable
agreement with the literature data from the analysis of color magnitude
diagrams of the objects.
