Testing broad line region models with Reverberation Mapping
  New reverberation mapping (RM) measurements, combined with accurate
luminosities and line ratios, provide strong constraints on the location of the
line emitting gas in the broad line region (BLR) of active galactic nuclei
(AGN). In this paper I present new calculations of radiation pressure and
magnetic pressure confined clouds and apply them to a ``generic AGN'' and to
NGC 5548. The new calculations are in good agreement with the observed lags of
all broad emission lines, and with the luminosities of La, Civ 1549, Ovi 1035
and Heii 1640. They are also in reasonable agreement with the luminosities of
Mgii 2798 and the 1990A blend of Ciii] and Siiii] lines for high metallicity
gas. They explain the changes in time-lag following an increase in continuum
luminosity and their dependencies on the inner and outer boundaries of the BLR.
They also predict very strong Balmer and Paschen continua with important
implications to continuum RM experiments. However, the calculated Balmer and
Paschen line luminosities are too weak, by factors of 2-5. This ``Balmer line
crisis'' was noted in several earlier works and is now confirmed and
constrained by RM measurements that were not available in the past. It seems
that present photoionization codes that use the escape probability formalism,
fail to correctly compute the Balmer line luminosities in high density, large
optical depth gas.
