Search

We report spectrophotometric observations made with SOFIA/FORCAST on 2011 June 2 UT. Optical measurements have previously shown that the abundance discrepancy factor (adf) varies with position in several high-adf PNe, and is highest close to the central star. The very low electron temperature inclusions postulated to explain the abundance discrepancy, must be cooled predominantly by fine structure IR lines. These SOFIA data will map mid-IR FS lines (and our related Herschel program will add several far-IR FS lines) in the bright, well-characterized, high-adf PN NGC 7009. We will compare these IR results with FS optical line measurements in order to correlate ratios of IR to optical fluxes with position, and thus correlate with where the adf peaks.

The emission‐line analysis of ionized gaseous nebulae such as planetary nebulae (PNe) and H II regions is one of the best established methods for obtaining the abundance of elements in our own and in external galaxies. Abundance studies of PNe reveal the composition of matter returned to the interstellar medium (ISM) after being processed by stellar nucleosynthesis, while those of H II regions provide a snapshot of the composition of the ISM in the latest episode of its evolution. We discuss current issues in these related fields, and show how concerted efforts from observational spectroscopy and detailed models have been instrumental in proposing solutions for outstanding problems in the astrophysics of photoionized nebulae, and could motivate developments on ISM chemical evolution topics. The potential of Greek astronomy in the pursuit of relevant research with modern local facilities such as the Aristarchos telescope is noted.