MINDS: JWST/NIRCam imaging of the protoplanetary disk PDS 70. A spiral accretion stream and a potential third protoplanet

Two protoplanets have recently been discovered within the PDS 70 protoplanetary disk . JWST/NIRCam offers a unique opportunity to characterize them and their birth environment at wavelengths that are difficult to access from the ground. We image the circumstellar environment of PDS 70 at 1.87\,upmu m and 4.83\,upmu m, assess the presence of Pa-alpha emission due to accretion onto the protoplanets, and probe any IR excess indicative of heated circumplanetary material. We obtained noncoronagraphic JWST/NIRCam images of PDS 70 within the MIRI mid-INfrared Disk Survey (MINDS) program. We leveraged the Vortex Image Processing (VIP) package for data reduction, and we developed dedicated routines for optimal stellar point spread function subtraction, unbiased imaging of the disk, and protoplanet flux measurement in this type of dataset. A radiative transfer model of the disk was used to separate the contributions from the disk and the protoplanets. We redetect both protoplanets and identify extended emission after subtracting a disk model including a large-scale spiral-like feature. We interpret its signal in the direct vicinity of planet $c$ as tracing the accretion stream that feeds its circumplanetary disk, while the outer part of the feature may rather reflect asymmetric illumination of the outer disk. We also report a bright signal that is consistent with a previously proposed protoplanet candidate enshrouded in dust near the 1:2:4 mean-motion resonance with planets $b$ and $c$. The 1.87\,upmu m flux of planet $b$ is consistent with atmospheric model predictions, but the flux of planet $c$ is not. We discuss potential origins for this discrepancy, including significant Pa-alpha line emission. The 4.83\,upmu m fluxes of planets $b$ and $c$ suggest enshrouding dust or heated CO emission from their circumplanetary environment. The use of image-processing methods that are optimized for extended disk signals on high-sensitivity and high-stability from JWST can uniquely identify signatures of planet--disk interactions and enable accurate photometry of protoplanets at wavelengths that are difficult to probe from the ground. Our results indicate that more protoplanets can be identified and characterized in other JWST datasets.