Star formation histories in galaxies : confrontation of theory and observation

Abstract

Population synthesis results for galaxy nuclei from Bica (1988) are compared to those derived from the evolutionary method developed by Arimoto and Yoshii (1986). The two different approaches are interfaced by means of theoretical M/Lv ratios for single generation stellar systems computed for differing ages. We conclude that results from the empírica) synthesis by Bica (1988) are compatible with chemical evolution models. In order to match the spectral distribution of red nuclei dominated by old stellar populations it is necessary to introduce in the evolutionary models a mechanism to cut down significantly residual star formation, otherwise the V flux contribution from young components would be too strong. In the case of bluer galaxy nuclei, the definite identification of a burst of star formation should be performed simultaneously in flux and mass fraction diagrams. The present study gives hints about the origin ofthe gas consumed in recent and intermediate age star formation events.