Test of the Formation mechanism of the Broad Line Region in Active
  Galactic Nuclei
  The origin of the Broad Line Region (BLR) in active galaxies remains unknown.
It seems to be related to the underlying accretion disk but an efficient
mechanism is required to rise the material from the disk surface without giving
too strong signatures of the outflow in the case of the low ionization lines.
We discuss in detail two proposed mechanisms: (i) radiation pressure acting on
dust in the disk atmosphere creating a failed wind (ii) the gravitational
instability of the underlying disk. We compare the predicted location of the
inner radius of the BLR in those two scenarios with the observed position
obtained from the reverberation studies of several active galaxies. The failed
dusty outflow model well represents the observational data while the
predictions of the self-gravitational instability are not consistent with
observations. The issue remains why actually we do not see any imprints of the
underlying disk instability in the BLR properties.
