Constraints on the radial distribution of the dust properties in the CQ Tau protoplanetary disk

Context. Grain growth in protoplanetary disks is the first step towards the formation of the rocky cores of planets. Models predict that grains grow, migrate, and fragment in the disk and predict varying dust properties as a function of radius, age, and physical properties. High-angular resolution observations at more than one (sub-)mm wavelength are the essential tool for constraining grain growth and migration on the disk midplane. Aims. We developed a procedure to analyze self-consistently multi wavelength (sub-)mm continuum interferometric observations of protoplanetary disks to constrain the radial distribution of dust properties. Methods. We apply this technique to existing multi frequency continuum mm observations of the disk around CQ Tau, a A8 pre-main sequence star with a well-studied disk. Results. We demonstrate that our models can be used to simultaneously constrain the disk and dust structure. In CQ Tau, the bestfitting model has a radial dependence of the maximum grain size, which decreases from a few cm in the inner disk (< 40 AU) to a few mm at 80 AU. Nevertheless, the currently available dataset does not allow us to exclude the possibility of a uniform grain size distribution at a 3σ level.