Optical Synthetic Spectra of Elliptical Galaxies

We present the first results from our population synthesis models of elliptical galaxies. In this paper, we concentrate upon the optical region of the spectrum (3000-7000 A). We model elliptical galaxies as coeval, single-metallicity stellar populations. Integrated spectra are constructed from synthetic spectra of the stars which lie along 6, 10 and 16 Gyr isochrones having [Fe/H]=+0.39, 0.00 and -0.47. Our oldest, solar-metallicity spectrum is found to be an excellent match to a spectrum of the E1/S0 galaxy NGC 4472. The broad-band colors measured from our models infer that the reddest E/S0 galaxies have [Fe/H]~+0.25, with bluer galaxies probably having lower metallicities rather than younger ages. In addition, the Lick indices derived from our synthetic spectra are compared to Worthey's (1994) models and the observed indices in elliptical galaxies.