HI spatial distribution in the galaxy NGC 3783

We have mapped the emission from atomic hydrogen at lambda = 21 cm from the galaxy NGC 3783 with the Australia Telescope Compact Array. Our main resul ts are: a) the HI morphology is irregular and perturbed, gathered in three blobs apparently unrelated to the optical morphology; b) the observed HI ve locity distribution indicates a normal disk in differential rotation with a constant velocity out to a radius of 160 " (30 kpc), c) the inclination of the disk is about 25 degrees with the kinematic major axis at a position a ngle slightly different from that of the stellar bar, d) the HI mass inside a radius of 18 " is only 2.1 x 10(7) M. f, the total HI mass within 180 " is 1.1 x 10(9) Mo and the dynamical mass is 2 x 10(11) M.. The bulk of the gas in NGC 3783 is outside the diameter of the stellar bar; e) Numerical si mulations of the gas flow in the barred potential derived from the red imag e indicate that the pattern speed is Omega(p) = 38 km/s/kpc: the ring of Ha : emitting regions encircling the bar would then correspond to UHR, and the H alpha accumulation in the center to a nuclear ring. Various possibilitie s are discussed to account for the active nucleus fuelling.