We present a model that relates the width of the broad emission lines of active galactic nuclei (AGNs) to the Keplerian velocity of an accretion disk at a critical distance from the central black hole. This critical distance falls in a region bounded on the inward side by the transition radius between the radiation pressure- and the gas pressure-dominated region of the accretion disk and on the outward side by the maximum radius below which a stabilizing, radially accreting and vertically outflowing corona exists. We show that in the framework of this picture, the observed range of Hβ FWHMs from broad-line to narrow-line type 1 AGNs is well reproduced as a function of the accretion rate. This interval of velocities is the only permitted range and goes from ~20,000 km s-1 for sub-Eddington accretion rates to ~1000 km s-1 for Eddington accretion rates.
The Astrophysical Journal
- Pub Date:
- February 2000
- ACCRETION DISKS;
- GALAXIES: ACTIVE;
- GALAXIES: QUASARS: EMISSION LINES;
- 11 pages, 2 figures. Accepted for publication in ApJL