2001A&A...372..463O

Spatial and kinematical correlations between the HI and ¹²CO(2-1) emission of the southern spiral galaxy NGC 4945 are studied with a common angular resolution of ∼23'' (corresponding to 750pc at D=6.7Mpc) and a velocity resolution of ∼7km/s. The 1.4GHz continuum emission is also observed. The HI kinematics yield a galaxy mass of ∼1.4x10¹¹M_☉ within radius R=380'', with molecular and neutral atomic gas each contributing ∼2%, respectively. A central continuum source of size 7.6x3.4'' (250x110pc) is enveloped by a molecular cloud of mass 1.5x10⁹M_☉ for R≤7.5'', and is rapidly rotating with V_rot∼160km/s. HI emission from the central region at velocities |V-V_sys|>200km/s may be related to optically detected gas that is believed to trace an outflow directed towards the halo. Nuclear HI absorption at V-V_sys~+80km/s suggests inflow towards the centre, that was so far only seen in molecular lines. HI features at each end of the major axis (|R|∼600'') are interpreted as spiral arms that are viewed tangentially and that also cause prominent emission features in the radio continuum, HI, and CO further inside the galaxy. A central elongated region showing non-circular motions is interpreted as a bar which fuels the nuclear starburst. The HI and CO position-velocity data have been analysed using linear resonance theory, and possible locations of resonances are identified.