AND ASTROPHYSICS Localised, high-speed flows

Abstract. The remarkable velocity structure of the different components of the hydrogen-deficient planetary nebulaAbell 78 have been revealed by obtaining spatially resolved profiles of the [O iii] 5007A ̊ line with theManchester echelle spectrometer combined with the 2.1 m San Pedro Mártir telescope. The outer, diffuse, hydrogen-rich, 12400 diameter shell is ex-panding radially at 40 km s−1. The irregular, knotty, hydrogen-deficient 8900 5200 inner shell has a similar overall expan-sion velocity but more complex kinematical structure. Similar to A 30, velocity ‘spikes ’ are found in the position-velocity arrays of [O iii] 5007A ̊ profiles from the inner shell. These ex-tend to a further −140 km s−1 than the radial velocity of the approaching side of this inner shell. The [O iii] 5007A ̊ bright, hydrogen-deficient core knots are distributed throughout an elongated disk expanding at 25 km s−1. There is kinematical evidence that ‘polar bul-lets ’ 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] 5007A ̊ 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 themass-loaded, shocked,wind from the central star. Key words: planetary nebulae: individual: Abell 78 – ISM: kinematics and dynamics – ISM: jets and outflow