Successful First Light for the VLT Interferometer C

Observations with 1.5-m-class ESO telescopes have contributed significantly to a much clearer understanding of the phenomenology of Active Galactic Nuclei (AGN) that has emerged over the past seven years. Long-slit spectra of good resolution and high s/n enable us to accurately measure emission-line parameters for a significant number of AGN. Combined with soft X-ray and UV line measures from Hubble Space Telescope, the data reveal a parameter space that distinguishes between the diverse classes of AGN and organises them in a way that promises to redefine the input to physical models. We suggest that this Eigenvector 1 (E1) parameter space may be as close as we will ever come to finding an H-R diagram for quasars. Several arguments suggest that the ratio of AGN luminosity to black hole mass (L/M ∝ accretion rate) convolved with the effects of source orientation drives the principal E1 correlation. While L/M sustains, in a sense, the H-R analogy beyond phenomenology, the role of orientation reflects the greater complexity inherent in the lack of spherical symmetry for AGN.