Comparing Hbeta Line Profiles in the 4D Eigenvector 1 Context
  We describe a 4D Eigenvector 1 (4DE1) space that serves as a surrogate H-R
diagram for quasars. It provides a context for describing and unifying
differences between all broad line AGN. Quasar spectra can be averaged in a
non-random way using 4DE1 just as stellar spectra can be averaged non-randomly
within the OBAFGKM classification sequence. We find that quasars with FWHM
H_beta less than (Population A) and greater than (Population B) 4000 km/s show
many significant differences that may point to an actual dichotomy. Broad line
profile measures and fits reenforce the idea of a dichotomy because they are
fundamentally different: Pop.A - Lorentzian-like and Pop.B - double Gaussian.
The differences have implications both for BH mass estimation and for
inferences about source structure and kinematics.
