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T. A. Boroson (NOAO)
The relationship in AGN between the physical parameters that govern the accretion process and their observable characteristics has been elusive. Recent indication that the mass of the accreting black hole is well correlated with the mass of the spheroidal component of the host galaxy allows a great step forward in making sense of the different kinds of active nuclei and their spectral appearance.
This study reports on an investigation of the relation between the deduced physical parameters and the observable properties such as radio-loudness and morphology, x-ray spectral index, and UV and optical emission line characteristics. Laor (2000) has deduced a statistical relationship between black hole mass and observable properties using calibration information drawn from measurements of a small sample of objects. Using this relationship, L/LEdd and black hole masses are calculated for the entire low-redshift PG sample. Comparison of these quantities with the spectral properties analyzed by Boroson and Green (1992) shows that the correlations known as eigenvector 1 are primarily driven by L/LEdd, while eigenvector 2 is primarily driven by luminosity. The two of these together determine the black hole mass.
This explanation leads to an appealing picture that explains the relationships among different types of AGN (e.g., Seyferts, radio-loud and -quiet quasars, radio galaxies), their properties, and the types and luminosities of the host galaxies in which they occur.