HIGH-RESOLUTION RADIO-CONTINUUM OBSERVATIONS OF COMPACT PLANETARY-NEBULAE

We report 15 GHz radio continuum observations of 19 compact planetary nebulae. The high resolution (approximately 0".1) images obtained allowed detailed examination of the structures of these nebulae. Most of these objects have very high radio surface brightness temperatures and critical frequencies, suggesting that they are very young planetary nebulae. Most show a "bipolar" central structure, consistent with an ellipsoidal shell viewed at an angle, and may also show extended halo structure outside of the shell, probably representing remnant material left over from the asymptotic giant branch progenitor.