Spatial segregation of dust grains in transition disks

We present spatially resolved observations of three protoplanetary disks with a dust depleted inner region (transition disks) using ALMA and SPHERE observations. To constrain the morphology of large and small grains probed by the two instruments, we performed radiative transfer modeling. Our models indicate that the millimeter-sized grains are less extended vertically and radially than the micron-sized grains, indicating advanced settling and radial drift. Moreover, to understand better the origin of transition disks cavities, we compare our results with a sample of 19 other transition disks observed with both ALMA and SPHERE. This analysis shows that, in general, the cavities observed in scattered light are smaller than the ones detected at millimeter wavelengths. The results indicate that 15 out of the 22 cavities in our sample are consistent with being caused by a planet while the other require the presence of a more massive companion or of several low-mass planets.