On Correlations between the Broad Absorption Lines and Adjacent Broad Emission Lines in QSO Spectra

Abstract

We compare the C IV broad absorption line (BAL) and broad emission line (BEL) properties in the sample of 72 BAL QSOs which have been studied by Korista and coworkers. A principal-component analysis and subsequent fits to some of the measured properties are utilized to derive quantitatively, for the first time, some empirical relationships between BAL properties and the adjacent BEL properties. The most interesting result stems from a correlation between the FWHM of the C IV BEL and both (1) the minimum outflow velocity of the generally detached BAL trough and (2) the outflow velocity at minimum BAL intensity. These correlations suggest that at least some type of secondary physical relationship exists between the gases in the BAL and BEL regions. This must be explained by any successful model for these regions. However, we find no correlation between continuum luminosity and BAL properties. This suggests that radiation pressure may not be a dominant force in driving the outflowing BAL region clouds.