Assigned ID: 687 ----- Submission 1 (Sat Jan 22 00:56:29 GMT 2005) ----- Planetary Nebulae (PNe), as the final phase of evolution for intermediate mass stars, are major contributors to the enrichment of the interstellar medium (ISM). In PNe, a hot central star illuminates a gas and dust shell which was ejected during earlier evolutionary phases. UV radiation from the star creates an ionized region bounded by neutral gas and molecules. A better understanding of the nature of the molecular and ionized gas envelopes of PNe is important to our understanding of the evolution of PNe and their contribution to the enrichment of the ISM. Knots and filaments in the ionized gas images of PNe are common, if not ubiquitous. Additionally, it has been shown that molecular gas exists inside dense condensations within the ionized regions, but the origins of these clumps are not known. We propose to study the morphologies of both molecular and ionized gas for five PNe that have been imaged by both WFPC2 and NICMOS (at the 2.12um H2 line). The structure and appearance of the knots in ionized and molecular gas for each PNe can be compared to assess the evolutionary status of the molecular clumps and how it is affected by the evolutionary status of the whole PN. This will aid our understanding of the origin of the molecular knots, and the enrichment of the ISM by dying intermediate mass stars.

ISM AND CIRCUMSTELLAR MATTER 12 33000 false 0.0 false false false false false SUPPORTED