The effects of compositional inhomogeneities and fractal dimension on the optical properties of astrophysical dust
D. Bazell, E. Dwek;
ApJ, 1990, 360, 142
ABSTRACT:Mathis and Whiffen (1989) have recently suggested that interstellar dust particles are fluffy aggregates of submicron-size particles
composed of various astronomical minerals.
These dust particles should
exhibit optical properties that are quite different from standard dust,
characterized by spherical particles of various homogeneous mineral
composition.
In this paper, the discrete dipole approximation (DDA) method is used to
examine the effects of chemical inhomogeneities and spatial structure on the
optical properties of interstellar Mathis-Whiffen-type dust
particles.
The spatial structure of the dust is represented by its fractal dimension,
and the chemical inhomogeneities are simulated by randomly assigning the
composition of the occupied sites in the structure to be either carbon or
silicate.
It is found that compositional inhomogeneities are the dominant
parameter affecting the shape of the 9.7 and 18 micron silicate bands.
Some
bands-shape variations can be attributed to the fractal dimension of the dust.
The
results derived here can be used to explain or constrain variations in these
parameters among various astronomical objects.
KEYWORDS: cosmic dust, fractals, interstellar matter, optical properties, abundance, spatial distribution
PERSOKEY:dust, SIZE DISTRIBUTION, ,
CODE: bazell90