Recently, we have found evidence for an offset active nucleus in the Seyfert 1 galaxy NGC 3227 (Mediavilla & Arribas 1993). In fact, it was found that the BLR is offset with respect to the kinematical centre derived from the ionized gas. This kinematical centre has a heliocentric radial velocity which is in good agreement with previous CO and HI determinations for the systemic velocity of the galaxy, suggesting that the BLR is not at the galactic mass centroid. In addition, some kinematical distortions are observed around the BLR which are probably related to the activity. Here we will give some additional details on the fit of the observational data to a simple model, and the proper location of the kinematical centre.

Introduction: bidimensional spectroscopy with optical fibres

Bidimensional spectroscopy with optical fibres is a new technique which allows two-dimensional mapping of spectral features. Using this technique we are carrying out a programme to study the circumnuclear environment of Seyfert galaxies. To this end, we have developed several optical fibre systems for their use with the telescopes at the Observatorio del Roque de los Muchachos, on La Palma. In particular, the HEXAFLEX system (Arribas, Mediavilla & Rasilla 1991; hereafter Paper I) was conceived for the Nasmyth focus of the 4.2-m, William Herschel Telescope (WHT). The 2d-ISIS works at the auxiliary focus of the WHT, and HEXAFLEX-II with the Nordic Optical Telescope (NOT).