We present the results obtained from an objective search for stellar clusters , both in the currently active nuclear starburst region , and in the post-starburst disk of M82 .
Images obtained with the Advanced Camera for Surveys ( ACS ) aboard the Hubble Space Telescope ( HST ) in F435W ( B ) , F555W ( V ) , and F814W ( I ) filters were used in the search for the clusters .
We detected 653 clusters of which 393 are located outside the central 450 pc in the post-starburst disk of M82 .
The luminosity function of the detected clusters show an apparent turnover at B=22 mag ( M _ { B } = -5.8 ) , which we interpret from Monte Carlo simulations as due to incompleteness in the detection of faint clusters , rather than an intrinsic log-normal distribution .
We derived a photometric mass of every detected cluster from models of simple stellar populations assuming a mean age of either an 8 ( nuclear clusters ) or 100 ( disk clusters ) million years old .
The mass functions of the disk ( older ) and the nuclear ( younger ) clusters follow power-laws , the former being marginally flatter ( \alpha = 1.5 \pm 0.1 ) than the latter ( \alpha = 1.8 \pm 0.1 ) .
The distribution of sizes ( Full Width at Half Maximum ) of clusters brighter than the apparent turn-over magnitude ( mass \gtrsim 2 \times 10 ^ { 4 } M \odot ) can be described by a log-normal function .
This function peaks at 10 pc for clusters more massive than 10 ^ { 5 } M \odot , whereas for lower masses , the peak is marginally shifted to larger values for the younger , and smaller values for the older clusters .
The observed trend towards flattening of the mass function with age , together with an over-abundance of older compact clusters , imply that cluster disruption in M82 is both dependent on the mass and size of the clusters .