Different Velocity Dependences of Physical Conditions of High- and   Low-Ionization Lines in Broad-Line Regions
  We present results from a study of high- and low-ionization emission line ratios as a function of projected velocity for a sample of eight active galactic nuclei (AGNs). Our results are based on analysis of high signal-to-noise optical and Hubble Space Telescope (HST) UV spectra. Comparing the emission line ratios to those predicted by photoionization models indicates that the physical conditions responsible for the high-ionization emission lines are consistent with a wind, whereas those of the low-ionization lines are consistent with a virialized disk. 
Stephanie A. Snedden and C. Martin Gaskell