SPECTRAL:: A new evolutionary synthesis code.: Application to the irregular Galaxy NGC 1560

We have developed a new evolutionary synthesis code, which incorporates the output from chemical evolution models. We compare results of this new code with other published codes, and we apply it to the irregular galaxy NGC 1560 using sophisticated chemical evolution models. The code makes important contributions in two areas: a) the generation of synthetic populations with time-dependent star formation rates and stellar populations of different metallicities; b) the extension of the set of stellar tracks from the Geneva group by adding the AGB phases for m(i)/M. > 0.8, as well as the low mass stars. Our code predicts spectra, broad band colors, and Lick indices by using a spectral library, covering a more complete grid of stellar parameters than previous models. The application of the code to the galaxy NGC 1560 constrains the star formation age of its stellar population at around 10.0 Gyr.