VLT-spectropolarimetry of the high-polarization Seyfert 1 galaxy Fairall 51

We present high-precision optical spectropolarimetry of the Seyfert 1 galax y Fairall 51 (F51) taken with FORS1 at the VLT. The observed spectrum shows unpolarized and linearly polarized components. The AGN continuum and the b road lines show (after correction for the Galactic interstellar polarizatio n and the light contribution of the F51 host galaxy) a practically identica l amount of intrinsic polarization ranging from 5% in the red to 13% in the UV. The narrow lines are unpolarized or show only little intrinsic polariz ation. The observed AGN continuum and the broad line radiation can be expla ined by a combination of reddened (and attenuated) direct light and scatter ed light reflected from an optically thin dust region. Hence, within the fr amework of the unification scheme of AGN, the Seyfert 1 galaxy F51 appears to be an example of a borderline Seyfert 1/Seyfert 2 case where the nucleus is partially obscured like for other type 1 AGN with high intrinsic scatte ring polarization. It is found that the scattering region in F51 is located far from the BLR and the continuum source. Thanks to this special scatteri ng configuration, we were able to study the kinematics (line profiles) of t he broad line region from two different viewing angles, one along the line of sight (in total light) and one via the scattering region (in polarized l ight). The line profiles in polarized and total light are found to be indis tinguishable to a very high accuracy, strongly indicating that the velocity field of the F51 BLR is essentially spherically symmetric.