Correlation among extinction efficiency and other parameters in an aggregate dust model

TL;DR

This study investigates how the extinction efficiency of porous dust aggregates correlates with their composition, size, and wavelength, providing new regression models for interstellar extinction across various parameters.

Contribution

First to analyze the correlation among extinction efficiency, dust composition, size, and wavelength in aggregate dust models, offering regression-based predictive relations.

Findings

Q_{ext} increases with n from 1.4 to 2.0 at fixed k

Correlation between Q_{ext} and n is linear for small clusters, quadratic for larger ones

Q_{ext} and k are polynomially correlated, degree depending on size and wavelength

Abstract

We study the extinction properties of highly porous BCCA dust aggregates in a wide range of complex refractive indices ($1.4 \le n \le 2.0$, $0.001 \le k \le 1.0$) and wavelength ($0.11\mu m \le \lambda \le 3.4\mu m$). An attempt has been made for the first time to investigate the correlation among extinction efficiency ($Q_{ext}$), the composition of dust aggregates ($n, k$), the wavelength of radiation ($\lambda$) and size parameter of the monomers ($x$). If $k$ is fixed at any value between 0.001 and 1.0, $Q_{ext}$ increases with increase of $n$ from 1.4 to 2.0. $Q_{ext}$ and $n$ are correlated via \emph{linear} regression when the cluster size is small whereas the correlation is \emph{quadratic} at moderate and higher sizes of the cluster. This feature is observed at all wavelengths (UV to optical to infrared). We also find that the variation of $Q_{ext}$ with $n$ is very small when $\lambda$ is high. When $n$ is fixed at any value between 1.4 and 2.0, it is observed that $Q_{ext}$ and $k$ are correlated via polynomial regression equation (of degree 1, 2, 3 or 4), where the degree of the equation depends on the cluster size, $n$ and $\lambda$. The correlation is linear for small size and quadratic/cubic/quartic for moderate and higher sizes. We have also found that $Q_{ext}$ and $x$ are correlated via a polynomial regression (of degree 3,4 or 5) for all values of $n$. The degree of regression is found to be $n$ and $k$-dependent. The set of relations obtained from our work can be used to model interstellar extinction for dust aggregates in a wide range of wavelengths and complex refractive indices.