Speaker
Description
High-resolution ALMA observations of protoplanetary disks commonly reveal multiple narrow rings. Surprisingly, many of these rings exhibit similar moderate optical depths (τ ≃ 0.2–0.5 at millimeter wavelengths), despite substantial variation in disk environments — a puzzling uniformity that hints at some underlying unknown effect regulating dust physics.
We propose that this “optical depth fine‑tuning” arises naturally from ongoing planetesimal formation via streaming instability. Using DustPy, our open-source Python package for gas and dust evolution in protoplanetary disks, we simulate radial drift, grain growth, fragmentation, and the conversion of pebbles into planetesimals once midplane dust-to-gas ratios exceed unity. Our simulations consistently reproduce ring optical depths in the observed range by converting excess dust into “invisible” planetesimals — without arbitrary opacity adjustments. These results support the hypothesis that disk rings regulate their optical depth through active planetesimal formation.
| Category | Disk substructures and implications |
|---|---|
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