Nature of the newly detected F480M residual emission in the PDS 70 disk gap

Determine whether the residual emission detected at 4.8 µm in JWST/NIRISS Aperture Masking Interferometry observations of PDS 70—located southwest of PDS 70 A with position angle approximately 220 degrees and an unconstrained separation within roughly 200 milliarcseconds—is produced by a compact source (e.g., an additional planet) or by an inner disk feature such as a localized structure in the inner disk.

Background

The study presents JWST/NIRISS AMI observations of the PDS 70 system at 4.8 µm, re-detecting protoplanets PDS 70 b and c and modeling disk emission. After fitting a two-planet-plus-disk model, the authors identify residual emission at signal-to-noise ratio around 4 located southwest of the star and near the inner working angle.

Nested sampling on the residuals yields a best-fit position angle near 220 degrees and indicates strong correlation between separation and contrast, leaving the separation imperfectly constrained. The position angle is not consistent with forward scattering from an inner disk with the same geometry as the outer disk, motivating the question of whether the feature is a compact source (e.g., a third planet) or a non-planetary inner disk structure.

References

However, due to the unconstrained nature of the separation of the emission it is unclear whether the signal is due to compact emission or an inner disk feature.

— The James Webb Interferometer: Space-based interferometric detections of PDS 70 b and c at 4.8 $μ$m  (2404.13032 - Blakely et al., 2024) in Subsection 4.2, Residual Signal and Contrast Limits