METALLICITY INDEXES FOR MULTIPOPULATION MODELS .1. THE GALACTIC BULGE

We report new spectroscopic observations on integrated light from the galactic bulge in Baade's window in the range 4700-6000 Angstrom. Meta llicity indices H beta, Mg-2, Mgb, Fe5270, Fe5335, and Na D were measu red. Foreground disk stars may certainly affect the hydrogen index, bu t their contribution to the magnesium and iron indices is probably sma ll. The velocity dispersion derived from the Fourier quotient method i s 112+/-14 km/s, in very good agreement with kinematical data from bul ge K giants, giving further support to the interpretation that the int egrated light is dominated by those stars. Multipopulation models synt hesizing the observed iron and magnesium indices indicate a mean metal licity [Fe/H]=-0.02, a mean abundance ratio [Mg/Fe]=+0.45, and a mean age of 14.0+/-1.2 Gyr for the bulk of the bulge stars. The derived met allicity and abundance of ''alpha elements'' (here represented by magn esium) are consistent with existing low-resolution spectra and photome tric data. (C) 1996 American Astronomical Society.