Constraints on the dust size distribution in the protoplanetary disk around HD 163296 by ALMA multi-band observations

speaker: Doi Kiyoaki


Dust in protoplanetary disks is the material for planets, and how the dust grows is a critical problem in planet formation. Recently, high-resolution observations by ALMA made it possible to spatially resolve the dust distributions in protoplanetary disks. To characterize the disk and dust particles, we focused on the wavelength dependency of the dust distributions. We analyzed Band 6 (1.3 mm) and Band 4 images of the disk around HD 163296 and constrained the dust radial and vertical distributions. The disk has two clear rings at 67 au and 100 au. We found that the ring width is similar between the 2 Bands at the inner ring, whereas the ring width is narrower at Band 4 than at Band 6 at the outer ring. These results suggest that the maximum dust size is smaller than the observed wavelength at the inner ring, whereas the maximum dust size is larger than the wavelength in the outer ring, assuming the dust trapping scenario. We also found that the dust is puffed up in the inner ring and settled in the outer ring at both wavelengths. They are consistent with the dust size suggested by the radial profile. This local variation of the dust size and distribution suggests the possibility that the planetesimal formation is a localized process.