Large-scale H I structure of the Circinus galaxy

HI observations with the Australia Telescope Compact Array (ATCA) are used to study the neutral gas distribution and kinematics of the Circinus galaxy . One of the most outstanding features of Circinus is its enormous size (at least 80 arcmin or nearly 100 kpc, assuming a distance of 4 Mpc) revealing a beautiful large-scale spiral pattern. The fit of a tilted-ring model to the velocity field reveals a strong kinematic warp of the outer spiral arms . The inner region (radius 250 arcsec or 5 kpc) contains a highly elongated structure with non-circular motions, suggesting that Circinus is a barred spiral galaxy. At the centre of Circinus there is a 50-arcsec or 1-kpc-radi us H I ring or disc rotating with a speed of at least 200 km s(-1).