The Organic Molecular Continuum: Bridging the Gap at Planetary Nebulae

The circumstellar envelopes of asymptotic giant branch (AGB) stars are known to be rich in carbon-bearing molecules. It has been thought that as these objects transition into planetary nebulae (PNe), the molecular material undergoes significant photodissociation. As a result, chemical content within subsequent diffuse clouds generally have to be rebuilt from atomic constituents, potentially delaying the emergence of organic molecules. Recent observations, however, contest this notion. The Submillimeter Telescope and 12m antenna of the Arizona Radio Observatory in conjunction with the Institut de radioastronomie millimétrique (IRAM) 30m telescope have been used to study planetary nebulae. Evidence from such sources demonstrate a persistent molecular presence (HC₃N, c-C₃H₂, and CCH, among others) over the lifespan of PNe, suggesting that they seed the interstellar medium with molecular material. The detections suggest a chemical link between evolved stars and diffuse clouds, in which the later inherit essential carbon-carbon bonds. In this talk, the current state of molecular chemistry in PNe will be presented, along with new results for select objects (e.g. M4-17 and M1-59). Spectra and abundances will be shown, illuminating the uninterrupted trajectory of interstellar molecules.