Determining the fraction of intrinsic C IV absorption in quasi-stellar object absorption-line systems

We present the results of an exhaustive study of QSO absorption line system s (QSOALSs) with respect to intrinsic QSO properties using an updated catal og of data in the literature. We have searched the literature for 6 and 20 cm radio flux densities and have studied 20 cm contour plots from the Faint Images of the Radio Sky at Twenty centimeters (FIRST) VL;A:Survey in order to compare the absorption properties with radio luminosity, radio spectral index, and radio morphology. Although the data in our catalog are decidedl y heterogeneous, great care has been taken to account for potential biases during the course of our research. Analysis of relatively unbiased subcatal ogs allows us to investigate the properties of QSOALSs with better statisti cs than with any single homogeneous catalog. This work focuses particularly on the nature of C rv QSOALSs and their ditribution in velocity space in l ight of intrinsic QSO properties. We find that the distribution of narrow,C Iv absorption systems with relative velocities exceeding 5000 km s(-1) is dependent not only on the optical luminosity of the QSOs but also on the ra dio luminosity, the radio spectral index, and the radio morphology of the Q SOs. These observations are apparently inconsistent with the hypothesis tha t these systems are predominantly due to intervening galaxies, and it would seem that the contamination of the intervening systems (from 5000 to 75,00 0 km s(-1)) by those that are intrinsic to the environment of the QSO is si gnificantly larger than expected. We stress the need for truly homogeneous and unbiased surveys of QSOALSs to confirm these results from our inhomogen eous data set.