Absorption mass opacities for each dust radius and filling factor. a) Parameter space in volume filling factor f against dust radius a to investigate mass opacity. The dotted lines correspond to b)−d). b) Absorption mass opacity when dust radius a changes while f = 1. c) When the dust filling factor changes while a = 1 mm. d) When both a and f change while af keeps constant. The constant af corresponds to the same mass-to-area ratio of the dust aggregates.