Extinction by porous silicate and graphite grains
نویسندگان
چکیده
Discrete dipole approximation (DDA) is used to calculate extinction efficiencies of porous silicate and graphite grains. We apply DDA first to the spheroidal solid grains assumed to be made of a large number of small scattering elements (dipoles). Then we systematically reduce the number of dipoles to model the porous grains. The extinction is studied as a function of wavelength, grain size and porosity for both silicate and graphite grains. Finally the extinction efficiencies of the porous silicate and graphite grains are used to evaluate the interstellar extinction curve which is found to fit well with the average observed extinction curve.
منابع مشابه
Interstellar extinction by porous grains
Interstellar extinction curve E(λ-V)/E(B-V) vs 1/λ is evaluated in the spectral range 3.4 μm and 0.1 μm using the extinction efficiencies of the porous silicate and graphite grains. The extinction efficiencies of the porous silicate and graphite grains are computed using the discrete dipole approximation (DDA). The model curves are compared with the average observed interstellar extinction curv...
متن کاملModeling Porous Dust Grains with Ballistic Aggregates I: Geometry and Optical Properties
We investigate the scattering and absorption of light by random ballistic aggregates of spherical monomers. We present general measures for the size, shape, and porosity of an irregular particle. Three different classes of ballistic aggregates are considered, with different degrees of porosity. Scattering and absorption cross sections are calculated, using the discrete dipole approximation (DDA...
متن کاملModeling Porous Dust Grains with Ballistic Aggregates I: Methods and Basic Results
We investigate the scattering and absorption of light by random ballistic aggregates of spherical monomers. We present a general measure for the porosity of an irregular particle. Three different classes of ballistic aggregates are considered, with different degrees of porosity. Scattering and absorption cross sections are calculated, using the discrete dipole approximation (DDA), for grains of...
متن کاملComposite Interstellar Grains
A composite dust grain model which is consistent with the observed interstellar extinction and linear polarization is presented. The composite grain is made up of a host silicate spheroid and graphite inclusions. The extinction efficiencies of the composite spheroidal grains for three axial ratios are computed using the discrete dipole approximation (DDA). The interstellar extinction curve is e...
متن کاملInterstellar Extinction by Spheroidal Dust Grains
Observations of interstellar extinction and polarization indicate that the interstellar medium consists of aligned non-spherical dust grains which show variation in the interstellar extinction curve for wavelengths ranging from NIR to UV. To model the extinction and polarization, one cannot use the conventional Mie theory which assumes the grains as solid spheres. We have used a T-matrix based ...
متن کامل