Nuclear and large-scale outflow in NGC 1808

Abstract

NGC 1808 has been studied via deep broad-band and H-alpha images and longslit spectroscopy around the Na I D and H-alpha lines. In particular, Na I is seen blueshifted in absorption and redshifted in emission, providing incontrovertible proof of outflow. B-R images show that the dust plumes associated with the outflow reach about 3 kpc or more above the plane. The morphology of the outflow is complex. Nuclear emission and absorption line profiles show pronounced blue wings similar to those seen in far-IR luminous galaxies (FIRGs), and indicate nuclear outflow velocities up to 700 km/s. The classification of NGC 1808 as a Seyfert 2 is reviewed and dismissed; rather, on the basis of line profiles and ratios and the presence of the 'superwind', NGC 1808 is probably an example of the FIRG phenomenon.