Temperature-dependent FIR/sub-mm dust emissivity indices: some implications for the diffuse ISM dust composition

Abstract

We have studied the effects of the laboratory-measured, temperature-dependent dust emissivity indices on the FIR/sub-mm emission properties of amorphous silicate and amorphous carbonaceous dust. When the experimentally-determined temperature dependence of the dust emissivity index is taken into account we find temperatures that can differ by as much as 1.5 K and emissivity indices that can differ by ~15%, with respect to the values obtained using published refractive index data as is to calculate these quantities. In addition, we find that the observed diffuse ISM dust temperature of ~17.5 K and emissivity index of 2 can seemingly be produced with a mixture of amorphous carbon and silicate grains only if temperature-dependent dust emissivity indices are adopted. We find that dust masses determined using the temperature-dependent dust emissivity indices are not significantly different from those derived using standard dust properties.