Dust in Dense Clouds

Abstract

Recent observational and theoretical studies of dust in dense clouds are reviewed with an emphasis on the growth of dust grains through accretion and coagulation. IR reflection nebulae around protostellar objects are useful probes of grain sizes in dense clouds. For example, detailed studies of the IR reflection nebula surrounding OMC 2-IRS 1 show that the (scattering) grains are much larger (≈ 5000 A) than in the diffuse interstellar medium. Likewise, the presence of a weak shoulder at 2.95 µm on the 3.08 µm feature in BN indicates the importance of scattering by icy grains and implies a very similar increase in the grain size.