How to determine the star formation histories in spiral disks

Abstract

We have computed 500 chemical evolution models for the galaxy NGC 4303. With the obtained evolutionary histories and a synthesis model we have also calculated the spectral indices Mg2 and Fe5270. Fom the 500 models, by using a chi-square technique, we obtain those reproducing the present day observations within a confidence level of 95 %, reducing the number of possible models to 19. Only 6 of them are also able to reproduce the spectral indices radial distributions with the same level of confidence. We conclude that this technique of combining chemical with evolutionary synthesis models is a very powerful tool, and, therefore, we propose to perform more observational campaigns to obtain these and other spectral indices in spiral and irregular galaxies.