An evaluation of spherically symmetric wind models for broad absorption line QSOs

The observed properties of QSOs exhibiting broad absorption lines in their spectra are described, and a class of models that consist of a spherical, outwardly accelerating wind maintained by constant mass-loss from a central continuum source are evaluated to acquire some general ideas about how broadened absorption features may or may not form. Line profiles are calculated for a wide range of parameter values, but are comparatively insensitive to the spatial scale of the system and to the velocity field parameters, other than the ratio of the initial outflow velocity to the maximum velocity attained. Line profiles from a cloud model exhibit the difficulties in obtaining sufficient obscuration of the core to produce the observed depth of absorption. Mass-loss rates may have to approach as much as 100 solar masses per year in models which take into account opacity to photoionizing radiation. An optically thick, continuous outflow model with a non-monotonic or decelerating velocity field looks promising.