BAL QSOs in the eigenvector 1 context: toward a self-consistent model of the line absorbing/emitting regions

Abstract

We attempt to define the structural properties of Broad Absorption Line (BAL) QSOs and their relationship with the general quasar population using the Eigenvector 1 correlations. We identify 8 low-redshift quasars (z $<$ 0.5, 6 with a BALnicity index $>$ 0 km s$^{-1}$) where it was possible to combine optical and UV spectroscopic observations. The special utility of low-$z$ quasars involves our ability to discuss CIV$\lambda$1549 BAL QSOs in the context of the Eigenvector 1 optical parameter space and to have a reliable measure of the quasar rest frame. We find that the majority of the BAL sources are population A sources as defined in Sulentic et al. (2000). At least 2 sources that are hosted by ultra-luminous IR galaxies show intriguing effects in their nuclear spectra. A possible correlation between the terminal velocity and luminosity L also suggests that the luminosity to black hole mass ratio ($L/M$) is a governing factor with the largest terminal velocity BALs showing the highest $L/M$ values. The CIV$\lambda$1549 emission line profiles of classical BALs show the ubiquitous E1 population A blue-shift that supports a disk+wind scenario with an opening angle of $<$ 45$^\circ$. Observation of “secondary” BAL features roughly in correspondence with the mean radial velocity of the CIV$\lambda$1549 emission motivates us to model the BAL systems with an additional component that may share the BLR outflow and may be co-axial with the accretion disk, perhaps associated to a significant black hole spin.