Size distribution of dust in the disk of β pictoris

Intensive studies of the P Pic dust disk, based on observational data from the visual to the far IR and mm, give a relatively good understanding of the global spatial dust distribution in the disk. In contrast, the size distribution of dust is poorly known-only some constraints on the grain sizes have been put so far. Assuming a continuous replenishment of larger grains from sources in the disk and a collisional production of smaller debris, and considering the dynamics of grains, we derive the size distribution of dust in a broad range from micron-sized grains to tiny nanometer-sized particles. We show that this dynamically justified size distribution explains the observed polarization and colors of the disk much better than commonly assumed single power-law distributions.