Atomic and molecular gas in the starburst galaxy NGC 4945

Spatial and kinematical correlations between the H I and (CO)-C-12(2-1) emi ssion of the southern spiral galaxy NGC4945 are studied with a common angul ar resolution of similar to 23" (corresponding to 750 pc at D = 6.7 Mpc) an d a velocity resolution of similar to7 km s(-1). The 1.4 GHz continuum emis sion is also observed. The Hi kinematics yield a galaxy mass of similar to1 :4 x 10(11) M-circle dot within radius R = 380", with molecular and neutral atomic gas each contributing similar to2%, respectively. A central continu um source of size 7."6 x 3."4 (250 x 110 pc) is enveloped by a molecular cl oud of mass 1.5 x 10(9) M-circle dot for R less than or equal to 7."5 and i s rapidly rotating with V-rot similar to 160 km s(-1). H I emission from th e central region at velocities \V-V-sys\ > 200 km s(-1) may be related to o ptically detected gas that is believed to trace an out ow directed towards the halo. Nuclear Hi absorption at V-V-sys similar to +80 km s(-1) suggests in ow towards the centre, that was so far only seen in molecular lines. Hi features at each end of the major axis (\R \ similar to 600") are interpre ted as spiral arms that are viewed tangentially and that also cause promine nt emission features in the radio continuum, H I, and CO further inside the galaxy. A central elongated region showing non-circular motions is interpr eted as a bar which fuels the nuclear starburst. The H I and CO position-ve locity data have been analysed using linear resonance theory, and possible locations of resonances are identified.