THE HISTORY OF STAR-FORMATION IN THE LOCAL DISC FROM THE G-DWARF METALLICITY DISTRIBUTION

We address the question of the occurrence of star formation bursts in the solar neighbourhood by using the metallicity distribution of the G dwarfs. We present a method to recover the star formation history usi ng simultaneously the metallicity distribution and the age-metallicity relation. The method associates the number of stars in a given metall icity interval with the corresponding time interval predicted by the a ge-metallicity relation. We take into account corrections relative to observational errors, cosmic scatter and scaleheight effects. The meth od is tested by simulations of the chemical evolution of a galaxy with irregular star formation rate, and our results show that it is possib le to recover the star formation history fairly well. The application of the method to the solar neighbourhood shows evidence for at least t wo strong events of star formation: a burst 8 Gyr ago, and a lull 2-3 Gyr ago. These features confirm some previous studies on the star form ation history in the local disc.