Angular-momentum delivery in infall-driven discs

Determine how the angular momentum of infalling material, including its coherence, spatial distribution, and alignment with the disc, controls instability strength, spiral morphology, warps, and misalignments in infall-driven protoplanetary discs.

Background

Mass loading from the parental envelope depends not only on the infall rate but also on how material enters the disc. The review highlights coherent streamers, spatially distributed infall, and aligned or misaligned angular momentum as physically distinct possibilities.

These properties can alter the induced instability and generate different observable structures. A systematic determination of this angular-momentum budget remains unresolved.

References

A second open question concerns the angular momentum budget of the infalling material itself. The outcome of mass loading depends sensitively on how and where material is injected into the disc: whether it arrives in a coherent streamer or distributed over an extended region, whether it is aligned or misaligned with the disc angular momentum vector.

— Gravitational instability in planet-forming discs  (2609.05080 - Longarini et al., 4 Sep 2026) in Section 5.1.1, Theoretical perspective, p. 20

What if the infall is not axisymmetric and/or torques the disc?

— From spirals to rings: dust dynamics in gravitoturbulent protoplanetary discs after late infall  (2609.10375 - Baruteau et al., 9 Sep 2026) in Section 5, Concluding remarks

However, no misaligned companion star (or planet) has been detected in this object, so it is unclear what is causing the disc to develop a twist.

— Disc breaking and parametric instability in warped accretion discs driven by differential precession  (2610.26184 - Held et al., 19 Oct 2026) in Section 7.1, “Astrophysical applications: wavelike regime”