New response functions for absorption-line indices from high-resolution spectra

Using a huge library of I-A resolution spectra over a wide range of log T-eff, log g and [Fe/H] and for both solar and a-enhanced abundance ratios [alpha/Fe], we derive the response functions (RFs) which are commonly used to correct indices with solar a-element ratios to indices with a-ratios >0. The RFs vary not only with the type of star but also with metallicity. With the aid of this and the fitting functions (FFs), we derive the indices for single stellar populations (SSP). They are used first to derive the age, metallicity, and degree of enhancement for sample of Galactic globular clusters for which these parameters have been independently derived from the colour-magnitude diagram and/or spectroscopic studies, and second to study the classical two index diagrams of early type galaxies.