Results of a homogeneous survey of absorption lines in QSOs of small and intermediate emission redshift

Results are presented for a spectroscopic survey of an intermediate (z(em) between 1.20 and 1.95) and low (z(em) between 0.40 and 1.20) redshift sample comprising 66 QSOs. The data indicate that the absorption systems in quasars have three different origins. Statistically, systems displaced by more than about 20,000 km/s from the emission redshift are due to intervening material; systems with z(abs) greater than z(em) have a velocity dispersion very similar to that expected if the absorbing material and the QSO are members of clusters of galaxies, and systems with an absolute value of less than about 3000 km/s for z(em) - z(abs) are interpreted to be predominantly associated with galaxy clusters. It is suggested that broad-line absorption systems are recently ejected gas which eventually evolves into multiple sharp-line systems. Attention is also given to the distribution of C IV and Mg II absorption systems in redshift.