New Empirical Fitting Functions of the Lick/IDS indices using MILES

Here we present new empirical fitting functions for the Lick/IDS line-strength indices as measured in MILES (Medium-resolution INT Library of Empirical Spectra; Sánchez-Blázquez et al., Cenarro et al. 2007). Following previous work in the field (Gorgas et al. 1993; Worthey et al. 1994; Worthey & Ottaviani 1997), these functions describe the empirical behavior of the line-strength indices with the atmospheric stellar parameters. In order to derive the fitting functions we have devised a new procedure which, being fully automatic, provides a better description of the line-strength index variations in the stellar parameter space.