Dust opacities for protoplanetary accretion disks: Influence of dust aggregates

In this paper, we study the influence of grain aggregation in the early phases of protoplanetary accretion disks on the dust opacities. We include olivine ([Fe,Mg]2SiO4), orthopyroxene ([Fe,Mg]SiO3), volatile and refractory organics, water ice, troilite (FeS), and metallic iron as major grain species and compare the results to the model with compact grains proposed by Pollack et al. (1994). We present both the wavelength-dependent mass absorption coefficients and the Rosseland mean opacities for different aggregation models. A major result is that the iron distribution in the different dust species plays a crucial role for the optical properties of the protoplanetary dust population. The Rosseland mean opacities for the recommended dust model with chemically inhomogeneous aggregates are summarized in a convenient analytical form.