Localised, high-speed flows within the hydrogen-deficient planetary nebula Abell 78

The remarkable velocity structure of the different components of the hydrogen-deficient planetary nebula Abell 78 have been revealed by obtaining spatially resolved profiles of the [O III] 5007Å line with the Manchester echelle spectrometer combined with the 2.1 m San Pedro Mártir telescope. The outer, diffuse, hydrogen-rich, 124″ diameter shell is expanding radially at 40 km s^-1. The irregular, knotty, hydrogen-deficient 89″ × 52″ inner shell has a similar overall expansion velocity but more complex kinematical structure. Similar to A 30, velocity 'spikes' are found in the position-velocity arrays of [O III] 5007Å profiles from the inner shell. These extend to a further -140 km s^-1 than the radial velocity of the approaching side of this inner shell. The [O III] 5007Å bright, hydrogen-deficient core knots are distributed throughout an elongated disk expanding at ≈ 25 km s^-1. There is kinematical evidence that 'polar bullets' are being ejected perpendicularly to this central feature at 380 km s^-1. Altogether 'velocity spikes' and other high-speed knots in the pv arrays of [O III] 5007Å profiles are found over a 455 km s^-1 range of radial velocities. Many of the kinematical phenomena are considered to be a consequence of the mass-loaded, shocked, wind from the central star.