Using Ringed Disks to Determine Fundamental Parameters of Planet Formation

Abstract Two nondimensional parameters, the Stokes number ( St ) and turbulent α , critically control the early stage of planet formation. In spite of their importance, these two numbers are notoriously difficult to obtain and they remain largely unconstrained, except in ringed disks. In particular, E. J. Lee (2024) showed that ringed disks can be uniquely leveraged to derive local St and α through a simple model combining the dust radial equation of motion with the measured distribution of dust masses in Class 0/I disks. We apply their model to the currently known census of ringed disks, finding 19 viable rings in 10 systems, which more than doubles the previous sample. Similar to previous findings, we obtain generally low St ∼ 10 −4 –10 −2 and α ∼ 10 −5 –10 −2 across a wide range of system parameters, consistent with all the disks that we study being rich in gas and the dust-to-gas ratio of the rings being too low to generate planetesimals. Disks around low-mass host stars likely have leakier traps, broadly consistent with massive, gap-carving giants being rare around low-mass hosts, if the rings are generated by planets.