Broad emission lines in QSO spectra

The broad optical emission lines in quasi-stellar objects (QSOs hereafter) are generally believed to originate in photoionized gas surrounding a powerful non-thermal radiation source. The emission-lines contain all the available information on the geometry, dynamics and physical conditions in the surrounding gas and their study is of primary importance in attempts to model the QSO phenomenon. The line profiles are studied both observationally and theoretically in this thesis. (author)