摘要：AbstractWe present evidence for two populations of quasars showing distinctly different broad line structure and kinematics. The first evidence for quasar dichotomy involve differences between radio-quiet and radio-loud sources. We proposed an alternate population A-B dichotomy based on optical, UV and X-ray spectroscopic properties. One of these populations (Pop. A: FWHM Hβ <4000 kms-1) is largely radio-quiet, while Pop. B (FWHM Hβ > 4000 kms-1) includes most radio-loud sources and a significant number of spectroscopically indistinguishable (as far as the low-ionization lines are concerned) radio-quiet sources. Comparison of multiwavelength measures for population A and B sources reveals more/larger differences than are found between radioquiet and radio-loud sources leading us to conclude that the population A-B distinction is more fundamental. The major physical driver of these differences is likely the Eddington ratio where the Pop. A sources show log L/LEdd= 0.2-1.0, and the Pop. B sources show log L/LEdd= 0.01-0.2 (for black hole masses logMBH≈ 8.5).
