The circumnuclear ring of ionized gas in NGC 3593

We present the results of narrow-band H+(N II) imaging of the early-type spiral NGC 3593 in combination with a study of the flux radial profiles of the (N II )( 654.80, 658.34 nm), H, and (S II )( 671.65, 673.08 nm) emission lines along its major axis. The galaxy is known to contain two counterro- tating stellar discs of different size and luminosity. We find that the H emission mainly derives from a small central region of 57 00 25 00 . It consists of a filamentary pattern with a central ring. This has a diameter of about 17 00 ( 0:6 h 1 kpc) and it con- tributes about half of the total H flux. The ring is interpreted as the result of the interaction between the acquired retrograde gas which later formed the smaller counterrotating stellar disc and the pre-existing prograde gas of the galaxy.