MINDS: JWST/NIRCam imaging of the protoplanetary disk PDS 70
arxiv(2024)
摘要
Context. 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 difficult to access from the
ground. Aims. We aim to image the circumstellar environment of PDS 70 at 1.87
μm and 4.83 μm, assess the presence of Pa-α emission due to
accretion onto the protoplanets, and probe any IR excess indicative of heated
circumplanetary material. Methods. We obtain non-coronagraphic JWST/NIRCam
images of PDS 70 within the MINDS (MIRI mid-INfrared Disk Survey) program. We
leverage the Vortex Image Processing (VIP) package for data reduction, and
develop dedicated routines for optimal stellar PSF subtraction, unbiased
imaging of the disk, and protoplanet flux measurement in this type of dataset.
A radiative transfer model of the disk is used to disentangle the contributions
from the disk and the protoplanets. Results. We re-detect 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 feeding 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 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 μm flux of planet b is consistent
with atmospheric model predictions, but not that of planet c. We discuss
potential origins for this discrepancy, including significant Pa-α line
emission. The 4.83 μm fluxes of planets b and c suggest enshrouding dust or
heated CO emission from their circumplanetary environment.
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