PDS 70 unveiled by star-hopping: total intensity, polarimetry and mm-imaging modeled in concert
arxiv(2024)
摘要
Context. Most ground-based planet search direct imaging campaigns use angular
differential imaging, which distorts the signal from extended sources like
protoplanetary disks. In the case PDS 70, a young system with two planets found
within the cavity of a protoplanetary disk, obtaining a reliable image of both
planets and disk is essential to understanding planet-disk interactions. Aims.
Our goals are to reveal the true intensity of the planets and disk without
self-subtraction effects for the first time, search for new giant planets
beyond separations of 0.1" and to study the morphology of the disk shaped by
two massive planets. Methods. We present YJHK-band imaging, polarimetry, and
spatially resolved spectroscopy of PDS 70 using near-simultaneous reference
star differential imaging, also known as star-hopping. We created a radiative
transfer model of the system to match the near-infrared imaging and
polarimetric data, along with sub-millimeter imaging from ALMA. Furthermore, we
extracted the spectra of the planets and the disk and compared them. Results.
We find that the disk is quite flared with a scale height of 15
edge of the disk at 90 au, similar to some disks in the literature. The gap
inside of 50 au is estimated to have 1
disk. The Northeast outer disk arc seen in previous observations is likely the
outer lip of the flared disk. Abundance ratios of grains estimated by the
modeling indicate a shallow grain-size index > -2.7, instead of the canonical
-3.5. There is both vertical and radial segregation of grains. Planet c is well
separated from the disk and has a spectrum similar to planet b, clearly redder
than the disk spectra. Planet c is possibly associated with the sudden flaring
of the disk starting at 50 au. No new planets > 5 Mj were found.
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