Determining the Fraction of Intrinsic CivAbsorption in Quasi‐stellar Object Absorption‐Line Systems

Abstract

We present the results of an exhaustive study of QSO absorption line systems (QSOALSs) with respect to intrinsic QSO properties using an updated catalog 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) VLA Survey in order to compare the absorption properties with radio luminosity, radio spectral index, and radio morphology. Although the data in our catalog are decidedly heterogeneous, great care has been taken to account for potential biases during the course of our research. Analysis of relatively unbiased subcatalogs allows us to investigate the properties of QSOALSs with better statistics than with any single homogeneous catalog. This work focuses particularly on the nature of C iv QSOALSs and their distribution in velocity space in light of intrinsic QSO properties. We find that the distribution of narrow, C iv absorption systems with relative velocities exceeding 5000 km s{sup {minus}1} is dependent not only on the optical luminosity of the QSOs but also on the radio luminosity, the radio spectral index, and the radio morphology of the QSOs. These observations are apparentlymore » inconsistent with the hypothesis that these systems are predominantly due to intervening galaxies, and it would seem that the contamination of the intervening systems (from 5000 to 75,000 km s{sup {minus}1}) by those that are intrinsic to the environment of the QSO is significantly larger than expected. We stress the need for truly homogeneous and unbiased surveys of QSOALSs to confirm these results from our inhomogeneous data set. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}« less