THE KINEMATICS OF THE IONIZED-GAS IN THE CIRCINUS GALAXY

The TAURUS-2 Fabry-Perot interferometer, mounted on the 3.9-m Anglo-Au stralian Telescope, has been used to observe the Circinus galaxy. We h ave mapped the intensity and velocity distribution of the ionized hydr ogen in the galaxy using the Balmer series H alpha spectral line. The semiresolved core (observed with a seeing disc of 30 pc) appears amorp hous in shape, which is commonly observed in Seyfert 2 galaxies. Its p eak coincides with the core position measured in the radio continuum, suggesting that ionized gas surrounds a non-thermal source. A circumnu clear ring or spiral of radius 220 pc and a relational velocity of 350 km s(-1) (assuming circular motions) surrounds the core. The inclinat ion angle of this feature, i =40 degrees +/- 10 degrees, is less than that of the previously observed radio continuum disc. The velocity cha nnel maps obtained for the H alpha ring show that the kinematics resem ble those of a rotating ring and the intensity displays a complex stru cture indicative of several, unresolved, H II regions. We believe the ring to represent a circumnuclear starburst. Our H alpha data also sho w the presence of the previously detected [O III] ionization cone to t he north-west of the core, measuring more than 400 pc in length. We su ggest that the ionization cone lies in a different plane from that of the starburst ring and is directed away from us. Several kinematic com ponents of the core are derived and we calculate an outflow velocity i n excess of 150-200 km s(-1) for gas above the core of Circinus, We al so present evidence for inflowing ionized gas at the centre of Circinu s. The correlation of the H alpha and radio continuum features is disc ussed, as well as the possible presence of a starburst-driven superwin d in the Circinus galaxy.