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

Tanuj Kumar Dhar, Himadri Sekhar Das


We study the extinction properties of highly porous Ballistic Cluster-Cluster Aggregate dust aggregates in a wide range of complex refractive indices (1.4 ≤ n ≤ 2.0, 0.001 ≤ k ≤ 1.0) and wavelengths (0.11 μm ≤ λ ≤ 3.4 μm). An attempt has been made for the first time to investigate the correlation among extinction efficiency (Qext), composition of dust aggregates (n, k), wavelength of radiation (λ) and size parameter of the monomers (x). If k is fixed at any value between 0.001 and 1.0, Qext increases with increase of n from 1.4 to 2.0. Qext and n are correlated via linear regression when the cluster size is small, whereas the correlation is quadratic at moderate and higher sizes of the cluster. This feature is observed at all wavelengths (ultraviolet to optical to infrared). We also find that the variation of Qext with n is very small when λ is high. When n is fixed at any value between 1.4 and 2.0, it is observed that Qext and k are correlated via a polynomial regression equation (of degree 1, 2, 3 or 4), where the degree of the equation depends on the cluster size, n and λ. The correlation is linear for small size and quadratic/cubic/quartic for moderate and higher sizes. We have also found that Qext 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.


light scattering — ISM: dust, extinction

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