DISTANCES FOR GALACTIC PLANETARY-NEBULAE .2. A SOUTHERN-HEMISPHERE SURVEY

We present integrated [O II] 3726, 3729-angstrom and [S II] 6716, 6731-angstrom doublet ratios and electron densities for 63 southern Galactic planetary nebulae (PN). We find that the densities derived from the integrated [O II] and [S II] doublet ratios are in excellent agreement with each other. We have derived distances to 57 of these objects, using recent calibrations based on observations of Magellanic Cloud PN. To derive distances to PN which are optically thin in the Lyman continuum, we use a variation on the Shklovsky constant ionized mass method which requires the electron density from the mean [O II] doublet ratios only and requires no knowledge of the nebular filling factor or angular diameter. For the optically thick PN, we have derived distances assuming constant Hbeta flux. This work follows on from Kingsburgh & Barlow (Paper I), where distances to 57 PN were derived. Filling factors, rms electron densities and absolute radii have also been derived for this southern sample. As in Paper I, we find that the derived filling factors decrease with increasing absolute angular radius, but again ascribe this result to the effects of measurement uncertainties in the adopted angular radii. Extended [O II] 3726, 3729-angstrom and [S II] 6716, 6731-angstrom emission surrounding 23 PN has been detected. We have derived upper limits on the electron densities for these extended regions and conclude that the emission originates from regions of diffuse Galactic background emission.