AGE AND ABUNDANCE EFFECTS IN SINGLE-STELLAR POPULATIONS

The present article proposes new fitting formulas for the indices Mg-2 and Na D as functions of stellar parameters but including explicitly the abundance ratio of the relevant element. Integrated metallicity in dices for single-stellar populations like, Mg-2, [Fe], Na D, H beta, a nd (B - V) color have been computed for a grid of 100 models as a func tion of age, metallicity, and relative abundances which stimulate a me dium enriched purely by type II supernova, or a mix of both types I an d II. Different diagrams show model self-consistency, in that most glo bular clusters appear to have ages larger than 12 Gyr and an average a bundance ratio [Mg/Fe]=0.34. Interpolation formulas based on our model computations are given for the different indices as functions of age, metallicity, and relative abundances (C) 1995 American Astronomical S ociety.