THE CIRCUMNUCLEAR REGION IN THE SEYFERT-1 GALAXY NGC-3227

This article presents H alpha and [O III] narrow-band images and long- slit optical and near-infrared spectroscopy at position angles 65.5 de grees and 25 degrees through the circumnuclear region in the Seyfert 1 galaxy NGC3227. After subtraction of a bulge + disc model, the contin uum image at lambda 5900 Angstrom shows an excess of emission aligned with the companion galaxy NGC 3226. We attribute this emission to a st ellar bar induced by the interaction. Along the leading parts of the b ar, we find dust lanes and 70 per cent of the H II regions detected in the disc. The H alpha and [O III] images show extended emission in th e circumnuclear region with very different morphologies. [O III] is el ongated to the north and nearly aligned with the bar. This emission is formed by two kinematical components, a broad component blueshifted w ith respect to a narrower component. The blue component could be photo ionized by radiation from the active nucleus, but the red component mi ght be associated with the starburst detected to the west. The H alpha image is aligned along PA = 65 degrees, and shows a bright knot at 4 arcsec south-west of the nucleus and a shell-like structure; there the line ratios can be fitted by photoionization by a stellar source. To the north-east, the spectrum shows characteristics of a high-excitatio n low-ionization nuclear emission region (LINER), and the line ratios can be explained as photoionization by a blackbody with a temperature of 140000K, ionization parameter 0.001, and solar chemical composition with an overabundance of N and S. Even though H alpha and [O III] pre sent different morphologies, both are extended 500 pc from the nucleus , inside the inner Lindblad resonance; this suggests that gravitationa l torques, associated with the non-axisymmetric potential produced by the bar and by interaction with the companion galaxy, transport the ga s to the inner Lindblad resonance (ILR), from where it fuels the circu mnuclear region in NGC 3227.