1996A&A...307..579M

Deep, narrow-band CCD images in the visible, nebular emission lines of the planetary nebula NGC 40, obtained with the San Pedro Martir telescope, have revealed the presence of two haloes to the barrel-shaped nebular core and a jet-like feature projecting from it. A faint, diffuse inner halo is ≃90" diameter whereas the outer halo has prominent filaments embedded in patchy emission within a region ≃4' diameter. Spatially resolved longslit spectra of the Hα and [N ii]6584 A emission lines have been obtained, using the Manchester echelle spectrometer combined with the Isaac Newton telescope, from the bright core of NGC 40, its two haloes and the jet-like phenomenon. Hundreds of times fainter C II 6578A profiles were obtained only from the bright core. The outer filamentary halo is shown to be relatively inert, emitting narrow, single lines on the systemic heliocentric radial velocity of -31km/s. Its internal turbulent motions are shown to be ≃7km/s and its electron temperature T_e=7400±160K. The nebular emission lines from the inner, diffuse, spherical halo are split in places by ≤50km/s which is approximately the splitting found over the bright nebular core. The jet-like feature is kinematically associated with the receding end of the barrel shaped core and does not have any of the kinematical characteristics expected of a true jet. The creation of all of these phenomena are discussed within current evolutionary models of planetary nebulae.