Statistics and mapping of asteroid concentrations in the proper elements space

A statistical investigation of asteroid families has been carried out using a new clustering technique, developed by A.I. Uavrishin. Proper elements for 2764 asteroids (1810 numbered and 954 PLS asteroids) have been computed. Using these data the Gavrishin z2 method gives only fifteen significant classes. Five of them are coincident with the Hirayama families, Themis, Eos, Coronis, Phocaea and Flora, that cannot be univocally subdivided. The new PLS families are clearly recognized. Furthermore many small sized families, reported by several authors, lose their statistical relevance. Isodensity maps of the asteroid belt and the distribution of the apparent mean opposition magnitude are also presented: they give an interesting representation of the internal structure of the main belt. Key Words: Asteroids - asteroid families - Kirkwood gaps - resonances