Model source functions S_ν of directly AGN-heated clouds for several different dust configurations (from left to right column: ISM standard configuration with Draine (2003) silicates, Ossenkopf et al. (1994) silicates, ISM large grains, and Graphite-dominated dust). Each row shows the emission of a cloud with τ_V = 50 at the given AGN distance r = r_sub (top), 10r_sub (middle) and 100r_sub (bottom), scaled to the total incoming flux of the AGN, F_AGN = L_bol/(4πr²). The corresponding hot-side temperature in units of T_sub = 1500K are also given. The various lines represent a specific phase angle, φ, of the cloud in steps of 30° (red: φ = 0°, i.e. full hot side; purple: φ = 180°, i.e. full cold side). For comparison, we overplotted the corresponding black-body emission B_ν(T) with the same temperature as the hot side of the cloud at the same distance from the AGN (dashed line).