How do single-peaked emission lines form if the gas is accreting in a disk?
A model using the disk wind’s opacity to form single-peaked lines has been proposed (Murray & Chiang 1997) as well as a cloud model that depends on the optical depth of the individual clouds (Bottorff et al. 1997). Recent work on this includes astro-ph/0405447, which proposes two separate regions for the BLR for producing the line cores (a spherical wind) and wings (an inner accretion disk).
