Sketch of a deeply embedded young star with a rotating accreting disk, disk wind, and an envelope (cocoon) with low-density polar cavities. Dust particles are assumed to be near the polar axis and walls of the cavity. Possible profiles of emission lines are shown for several viewing conditions: direct (A) and scattered (B and C) radiation from the central object, which consists of the star, and its surrounding emitting region (e.g., disk and disk wind region). Here I_e is the emergent radiation from this central object, and  are the radiation scattered by the dust particles in cases B and C respectively, τ_A, τ_B and τ_C are the optical thickness of the circumstellar envelope at different heights above the disk (τ_B ≪ τ_A and τ_C ≪ τ_A), i is the viewing angle, i′ is the angle between the polar axis and direction to the scattering particle, and θ is a geometrical parameter.