Molelling insterstellar extinction using aggregate dust model

Abstract

In this work, we consider the aggregate dust model to study the extinction efficiency (Qext) of interstellar dust in the wavelength range 0.11 - 3.4 µm. Using Superposition T-matrix code with Ballistic Cluster-Cluster Aggregate (BCCA) having 64 number of monomers and a well defined size distribution within a size range 0.004 to 0.25 micron, the normalized average extinction curves are generated for astronomical silicate, graphite and amorphous carbon. The well pronounced UV bump can be noticed for graphite grains at 2175Å. It is observed that for large size of the graphite grain, the UV-bump almost disappear. Moreover the nature of variation of extinction curve with increasing size of the grain is also studied. We then try to regenerate the observed extinction curve in the wavelength range 0.11 - 3.4 µm considering suitable mixing among silicate, graphite and amorphous carbon. It is found from our work that the observed interstellar extinction curve can be successfully reproduced using the proposed aggregate dust model with 45% silicate, 40% graphite and 15% amorphous carbon in the total mixture.