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Constrains on PDS 70 b and c from the dust continuum emission of the circumplanetary disks considering in situ dust evolution

Presentation #621.13 in the session Protoplanetary Disks - Observations.

Published onApr 03, 2024
Constrains on PDS 70 b and c from the dust continuum emission of the circumplanetary disks considering in situ dust evolution

The young T Tauri star PDS 70 has two gas accreting planets sharing one large gap in a pre-transitional disk. Dust continuum emission from PDS 70 c has been detected by Atacama Large Millimeter/submillimeter Array (ALMA) Band 7, considered as the evidence of a circumplanetary disk. However, there has been no detection of the dust emission from the CPD of PDS 70 b. We constrain the planet mass and the gas accretion rate of the planets by introducing a model of dust evolution in the CPDs and reproducing the detection and non-detection of the dust emission. We first develop a 1D steady gas disk model of the CPDs reflecting the planet properties. We then calculate the radial distribution of the dust profiles considering the dust evolution in the gas disk and calculate the total flux of the dust thermal emission from the CPDs. We find positive correlations between the intensity of the dust emission and three planet properties, the planet mass, gas accretion rate, and their product called MMdot. We then find that the MMdot of PDS 70 c must be larger than 0.4 MJ2/yr, corresponding to the lower limits of the planet mass and the gas accretion rate, 5 MJ and 0.02 MJ/yr. This is the first case to succeed in obtaining constraints on planet properties from the dust continuum emission of a CPD. We also find some loose constraints on the properties of PDS 70 b from the non-detection of its dust emission. We propose possible scenarios for the PDS 70 b and c explaining the non-detection respectively detection of the dust emission from their CPDs. The first explanation is that planet c has larger planet mass and/or larger gas accretion rate than planet b. The other possibility is that the CPD of planet c has a larger amount of dust supply and/or weaker turbulence than that of planet b. If the dust supply to planet c is larger than planet b due to its closeness to the outer dust ring, it is also quantitatively explained why planet c has weaker Hα line emission than planet b by considering the dust extinction effect.

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