MANTA-Ray: Supercharging Speeds for Calculating the Optical Properties of Fractal Aggregates in the Long-Wavelength Limit

TL;DR

MANTA-Ray is a fast, versatile analytical model that accurately estimates the optical absorption of fractal dust particles in protoplanetary disks, significantly reducing computational time compared to traditional methods.

Contribution

The paper introduces MANTA-Ray, a novel analytical model that approximates absorption efficiencies of non-spherical dust aggregates with high accuracy and vastly improved speed over existing rigorous methods.

Findings

MANTA-Ray achieves 10-20% accuracy compared to DDA calculations.

The model is 10^13 times faster than discrete dipole approximation.

It works across all wavelengths and particle sizes in the long-wavelength regime.

Abstract

Correctly modelling the absorptive properties of dust and haze particles is of great importance for determining the abundance of solid matter within protoplanetary disks and planetary atmospheres. Rigorous analyses such as the discrete dipole approximation (DDA) can be used to obtain accurate absorption cross-sections, but these require significant computing time and are often impractical to use in models. A simple analytical equation exists for spherical particles in the long-wavelength limit (where the wavelength is much larger than the size of the dust particle), but we demonstrate that this can significantly underestimate the absorption. This effect is found to depend strongly on refractive index, with values of m = 1 + 11i corresponding to an underestimate in absorption by a factor of 1,000. Here we present MANTA-Ray (Modified Absorption of Non-spherical Tiny Aggregates in the RAYleigh regime): a simple model that can calculate absorption efficiencies within 10-20% of the values predicted by DDA, but 10^(13) times faster. MANTA-Ray is very versatile and works for any wavelength and particle size in the long wavelength regime. It is also very flexible with regards to particle shape, and can correctly model structures ranging from long linear chains to tight compact clusters, composed of any material with refractive index 1+0.01i < m < 11+11i. The packaged model is provided as publicly-available code for use by the astrophysical community.