Spectropolarimetry of the borderline Seyfert 1 galaxy ESO 323-G077

Abstract

We report the detection of high linear polarization in the bright Seyfert 1 galaxy ESO 323-G077. Based on optical spectropolarimetry with FORS1 at the VLT we find a continuum polarization which ranges from 2.2% at 8300 Å to 7.5% at 3600 Å. Similar amounts of linear polarization are found for the broad emission lines, while the narrow lines are not polarized. The position angle of the polarization (θ = 84°) is independent of the wavelength and found to be perpendicular to the orientation of the extended [O III] emission cone of this galaxy. Within the standard model of Seyfert nuclei the observations can be well understood assuming that this AGN is observed at an inclination angle where the nucleus is partially obscured and seen mainly indirectly in the light scattered by dust clouds within or above the torus and the illuminated inner edge of the dust torus itself. Hence we conclude that ESO 323-G077 is a borderline Seyfert 1 galaxy which can provide important information on the geometric properties of active nuclei.