183 GHz H₂O emission towards NGC 4945: (top) data were binned to 40 km s^-1 resolution; (bottom) data were binned to 25 km s^-1 resolution. The red arrow indicates the approximate galactic systemic velocity of 556 km s^-1. The dashed lines indicate the velocity range of 22 GHz H₂O megamaser emission determined by Greenhill et al. (1997), about 410 to 800 km s^-1. The velocities are radio heliocentric in Greenhill et al. (1997) and so we use v_LSR = v_hel−4.6 km s^-1 to convert velocities. The black arrow denotes the velocity of a marginally significant feature in the 321 GHz spectrum reported by Hagiwara et al. (2016) (the strongest features at 321 GHz occurred between about 650 to 750 km s^-1). The velocity scale is radio LSR.