Dependence of light scattering properties on porosity, size and composition of dust aggregates

Abstract

In this work, we study the light scattering properties of dust aggregates (0.7µm R c 2.0µm) having a wide range of porosity (P = 0.59 to 0.98). The simulations are executed using the Superposition Tmatrix code with BCCA, BA, BAM1 and BAM2 clusters of varying porosity. We investigate the nature and dependencies of the different scattering parameters on porosity, size and composition of the aggregated particles for wavelengths 0.45 µm and 0.65 µm. We find that the scattering parameters are strongly correlated with the porosity of the aggregated structures. Our results indicate that, when the porosity of the aggregates decreases, keeping characteristic radius of the aggregates (R c ) same for all structures, there is an enhancement in the negative polarization branch (NPB) which is accompanied by a substantial increase in the anisotropies present in the material. Also at the exact backscattering region, the anisotropies are found to be linearly correlated with the porosity of the aggregated structure. The computational study reveals that, for low absorbing materials (k ≤ 0.1), the negative polarization minimum (P min ) is strongly correlated with the associated anisotropies. Finally, we put forward a qualitative comparison between our computationally obtained results and some selected data from the Amsterdam Light Scattering Database for both low and high absorbing materials. The experimental results also suggest that an increase in the NPB is always accompanied by an enhancement in the anisotropy at the backscattering region.

The size of monomers of dust aggregates in planet-forming disks

“…Observations of polarized scattered light from planetforming disks would be crucial in attempting to gain clarity on the monomer size. The scattering polarization properties of large porous aggregates have been suggested to strongly reflect the properties of the monomer, as reported in numerical simulations (West 1991;Kozasa et al 1993;Lumme et al 1997;Petrova et al 2000Petrova et al , 2004Kimura 2001;Kimura et al 2006;Bertini et al 2007;Kolokolova & Kimura 2010;Tazaki et al 2016;Min et al 2016;Halder et al 2018) and laboratory experiments (Zerull et al 1993;Gustafson & Kolokolova 1999; Observed maximum polarization fractions P obs max of several planet-forming disks. References: HD 142527 (Hunziker et al 2021), HD 169142 (Tschudi & Schmid 2021), HD 34700 A (Monnier et al 2019), GG Tau (Silber et al 2000), AB Aur (Perrin et al 2009), UX Tau A (Tanii et al 2012), TW Hya (Poteet et al 2018), HL Tau nebula region (Murakawa et al 2008), and AU Mic (Graham et al 2007).…”

Effect of dust size and structure on scattered-light images of protoplanetary discs

“…Since light scattering properties sensitively depend on size, structure, and composition of dust particles (e.g., Shen et al 2008Shen et al , 2009Paper I;Paper II;Halder et al 2018;Ysard et al 2018), disc scattered light may provide information of dust properties. Since disc scattered light has been commonly detected in optical-and near-infrared-wavelengths, in this study, we investigate a connection between dust properties and near-infrared disc scattered light.…”

Scattering properties of protoplanetary dust analogs with microwave analogy: Aggregates of fractal dimensions from 1.5 to 2.8

“…More information can be found in, for example, Min et al (2016); Tazaki et al (2016); Tazaki & Tanaka (2018), where different scattering methods such as discrete dipole approximation (DDA), T-matrix, or approximated methods were used. Similarly, the scattering properties of interplanetary dust and cometary particles were studied by Kimura et al (2016); Lasue & Levasseur-Regourd (2006); Lasue et al (2007) and Halder et al (2018), and atmospheric aerosols by Sorensen et al (2017Sorensen et al ( , 2018, and Liu & Mishchenko (2018).…”