2012MNRAS.425.2197A

We present high-resolution, long-slit spectroscopic observations of five compact ( ≤ 10arcsec) planetary nebulae located close to the galactic bulge region and for which no high spatial resolution images are available. The data have been drawn from the San Pedro Mártir kinematic catalogue of galactic planetary nebulae. The central star in four of these objects (M1-32, M2-20, M2-31 and M3-15) is of Wolf–Rayet (WR) type and the fifth object (M2-42) has a weak emission-line star (wels) type nucleus. These observations reveal the presence in all of them of a dense and thick equatorial torus-like component and high-speed, collimated bipolar outflows. The code SHAPE is used to investigate the main morphokinematic characteristics and reproduce the three-dimensional structure of these objects assuming a cylindrical velocity field for the bipolar outflows and a homologous expansion law for the torus/ring component. The deprojected expansion velocities of the bipolar outflows are found to be in the range 65–200km/s, whereas the torus/ring component shows much slower expansion velocities, in the range 15–25km/s. It is found that these planetary nebulae have very similar structural components and the differences in their emission-line spectra derive mostly from their different projections on the sky. The relation of their morphokinematic characteristics with the WR-type nuclei deserves further investigation.