10:45 AM - 11:00 AM
[PCG22-06] Absorption and scattering of dust particles in millimeter wavelength
Keywords:Protoplanetary disks, Dust particles, Optical properties, ALMA
First of all, I will talk about how dust structure and composition affect the absorption opacity in the Rayleigh domain. It is known that coagulated dust aggregates in the Rayleigh domain tend to show large absorption opacity compared to that of the mass-equivalent sphere obtained by the Mie theory. This enhanced absorption effect is due to the aggregate structure. In order to estimate the enhanced absorption of coagulated dust aggregates quantitatively, we perform numerical calculations of absorption opacity of dust aggregates, where we take into account higher order of multipole expansion of the electromagnetic field. As a result, it is found that absorption opacity at millimeter wavelength will be enhanced by a factor of two (four) for silicate (amorphous carbon) compared to the opacity of mass-equivalent sphere obtained by the Mie theory. In addition, it is also found that this enhancement becomes large for fluffy dust aggregates compared to compact dust aggregates. Next, I discuss scattering properties of dust particles. Scattering properties of dust particles have been intensively studied in visible and infrared wavelengths. I will summarize some studies about scattering properties of dust particles in visible and infrared wavelengths including our numerical studies, observations of circumstellar disks (protoplanetary disks and debris disks), and laboratory experiments, and discuss potential candidates of particle models that might explain millimeter-wave scattering polarization of protoplanetary disks.