AUTOMATED IDENTIFICATION OF OB ASSOCIATIONS IN M31

A new identification of OB associations in M 31 has been performed usi ng the PLC technique of Battinelli (1991). We found 174 associations w ith a very small contamination (< 5%) by random clumps of stars. The e xpected total number and average size of OB associations in the region of M 31 covered by our data set (Magnier et al. 1992) are approximate ly 280 and approximately 90 pc, respectively. M 31 associations theref ore have sizes similar to those of OB associations observed in nearby galaxies, so that we can consider them to be classical OB associations . This list of OB associations will be used for the study of the spati al distribution of OB associations and their correlation with other ob jects. Taking into account the fact that we do not cover the entire di sk of M 31, we extrapolate a total number of association in M 31 of ap proximately 420.