Dynamics and relevance of the opacity-driven insufficient-cooling regime

Investigate the nonlinear dynamics of the regime in which strongly temperature-dependent dust opacity under optically thick conditions may prevent clumps from cooling sufficiently to fragment, and determine whether this regime is realized in realistic protostellar disks.

Background

When opacity increases steeply with temperature, clump cooling in optically thick gas can be strongly suppressed during contraction, potentially preventing fragmentation through the stochastic-cooling pathway described in this work. The authors identify this as a qualitatively different regime not covered by their theory.

Understanding the dynamics of this regime and assessing its occurrence in real disks are crucial for robust fragmentation criteria under realistic dust opacities.

References

The dynamics of this regime, and whether it is relevant for realistic protostellar disks, will be left for future studies.

— Global Simulations of Gravitational Instability in Protostellar Disks with Full Radiation Transport. I. Stochastic Fragmentation with Optical-depth-dependent Rate and Universal Fragment Mass  (2410.12042 - Xu et al., 2024) in Section 4.4

The dependence of planet formation on disc microphysics also deserves further investigation. In particular, the sensitivity of the outer-disc formation regime to the assumed grain opacity and the physical processes that determine its value in realistic protoplanetary discs remain poorly constrained.

— Beyond Pebble Isolation: Diverse Pathways to Giant Planet Formation Across Stellar and Orbital Scales  (2609.09382 - Peerani et al., 8 Sep 2026) in Section 7, “Limitations and Future Work”