A&A Supplement series, Vol. 121, March 1997, 461-487
Received February 29; accepted June 20, 1996
M.C. Recondo-González
, W. Wamsteker
, J.
Clavel
, P.M. Rodríguez-Pascual
,
R. Vio
, Wang Ting-gui
, M. Santos-Lleó
,
and F. Makino
Send offprint request: G. Wuchterl
ESA IUE Observatory, Apartado 50727, 28080-Madrid, Spain
ISO Observatory, Astrophysics Division of ESA, Apartado 50727,
28080-Madrid, Spain
Astronomy department, University of Padua, Vicolo del Osservatorio 5,
35122 Padva, Italy
LAEFF, Apartado 50727, 28080-Madrid, Spain
Center for Astrophysics, University of Science and Technology of
China, Hefei, 230026-Anhui, P.R. China
Affiliated to the Astrophysics Division, Space Science Department, Noordwijk, The Netherlands
Institute of Space and Astronautical Science, 3-1-1,Yoshinda,
Sagamihara-shi, Kanagawa 229, Japan
The large amplitude of the variations of the Seyfert I Galaxy Fairall-9 between 1978
and 1991 make this Active Galaxy especially suitable for a combined study in terms
of reverberation analysis and photoionization modeling over the velocity field of the
broad lines of its ultraviolet spectrum. We have combined our ultraviolet
data with those available at other wavelengths to derive the intrinsic ionizing
continuum and to compare the predictions of the photoionization models with the
observations. The UV continuum varies with a factor of
on a characteristic time scale of 182 days. The intrinsic spectral
index UV-optical is 
and the optical variations do
not lag behind the UV variations at the mean sampling interval of 96
days. In the near IR, the J band flux presents a direct extension of the
UV-optical continuum (
). Only at low
flux levels is the 
flux proportional to the UV continuum, at
higher UV flux levels proportionality between the X-rays and the UV brightness
breaks down. The continuum spectral energy distribution (SED) of the nucleus
supports the previously reported FIR-NIR excess associated with 0.02
dust at a distance of some 
, as
well as a soft X-ray excess, possibly associated with the reprocessing on an
accretion disk of the hard X-rays emitted from a region above the disk. The
presence of strong Fe K
line in the GINGA spectra of this galaxy does
lend support to this model.
Line profile variability has been used to isolate four gaussian
line components, which are sufficient to describe all
lines at all levels of brightness in a consistent way: one narrow (i.e. unresolved at the
IUE resolution), and three broad components: a central (velocity same as the narrow
line), a red shifted (
) and a blue shifted (
) one. The three broad components are strongly correlated with the
UV continuum, indicating that photoionization is the dominant mechanism in the
BLR. Correlation analysis shows different delays between the
broad components and the UV continuum: respectively, 
, 
and 
for the central, red and blue one. Only the red
component of 
and 
appear to vary linearly with the continuum and give
significant transfer functions. The resulting transfer functions are peaked at
zero days delay and are unresolved at the average time resolution (96 days) of
our data. The photoionization models (CLOUDY) applied to the line ratios in
these components, indicate that the Broad-Line-Region (BLR) is situated
between 
from the ionizing source, with an hydrogen
density of 
, a column density of 
and a covering factor of 
, with an ionization parameter
between 0.003 and 0.089. However, no optically thick model reproduces the
/CIV and 
/NV ratios. From these results we propose a model for the
structure and dynamics of the BLR: the mass of the central compact object is M
. Around this exist two distinct gas
zones within the BLR: the gas producing the central component at 
light-days and gas, emitting the red and the blue components, at 
light-days moving inward to a central source. These results require that
both these gas zones be localized along the line-of-sight or, alternatively,
that the continuum emission must be strongly anisotropic. Besides, the gas
emitting the central component is most likely mixed with the dust and the
central gas to dust mass ratio is Mass (central gas)/mass(dust) = 100 - 750.
keywords: galaxies: individual (Fairall 9) -- galaxies: Seyfert -- ultraviolet: spectra