Modeling (Sub-)millimeter Scattering Properties of Fractal and Consolidated Porous Particles: Applications to Protoplanetary Disks

Abstract

We perform light-scattering numerical simulations for two dust populations: (i) consolidated porous particles computed with the discrete dipole approximation (ADDA) and (ii) highly porous aggregate models, including fractal and hierarchical aggregates, computed with the multiple-sphere T-matrix method (MSTM). Using DSHARP optical constants, we compute scattering matrices, cross sections, and effective albedo omega_eff for a size distribution n(a) proportional to a^q, with q = -3.5, amin = 0.1 micron, and ten wavelengths from 0.87 to 10 mm. We find that increasing porosity strengthens forward scattering and enhances polarization near theta approximately 90 degrees. For compact spheres, P(90 degrees) times omega_eff peaks near amax approximately lambda divided by 2 pi and then declines, whereas porous particles show a broader peak extending to larger sizes, keeping polarization-based constraints compatible with amax approximately 1 mm. Porosity also lowers kappa_abs at fixed dust mass relative to compact spheres, implying larger inferred dust masses for a given continuum flux.