Left: mass opacities for scattering κ_sca (short-dashed ocher), absorption κ_abs (long-dashed red), and extinction κ_ext = κ_abs + κ_sca (solid blue) for a dust model with grain sizes between a_min = 5 nm and a_max = 6 μm, leading to anopacity index of β = 0.8. The shaded areas indicate the wavelength regimes where dust polarization may be dominated by dichroic extinction (light blue), scattering (light yellow), and emission (light red). The shaded areas are estimated under the assumption that the product of dust number density ρ_dust and path length ℓ gives ρ_dust × ℓ ≈ 1 g cm⁻² (see Sect. 4.6 and Reissl et al. (2014) for further details). Right: same as the left panel, but with an upper grain size of a_max = 100 μm, corresponding to an opacity index of β = 1.3.