Constraining the turbulence and the dust disk in IM Lup: Onset of planetesimal formation

Context. Observations of protoplanetary disks provide information about the processes planetary formation and reasons behind diversity systems. The key to understanding is study dust evolution from small grains pebbles. Smaller (~1 µm) are well coupled gas dynamics their distribution significantly extended above disk midplane. Larger settle much faster efficiently formed only in By combining near-infrared polarized light millimeter observations, it possible constrain spatial both large grains. Aims. Our aim construct detailed models size vertical radial structure particles based on observational data. In particular, we interested recovering IM Lup disk. Methods. We created a physical model for disks. then simulated radiative transfer continuum radiation. Using Markov chain Monte Carlo method, compared derived images observations available best recover grain distribution. Results. emission tightly mass our model. find segregation distribution, with millimeter-sized These disk, possibly by sedimentation-driven coagulation, accordance short settling timescales predicted This also suggests high dust-to-gas ratio at smaller radii midplane, triggering streaming instabilities planetesimal inner obtained turbulent α parameter 3 × 10 −3 .