Spitzer Infrared Spectrograph (IRS) observations of Large Magellanic Cloud planetary nebula SMP 83

The first observations of the infrared spectrum of the LMC planetary nebula SMP 83 as observed by the recently launched Spitzer Space Telescope are presented. The high-resolution (R similar to 600) spectrum shows strong emission lines but no significant continuum. The infrared fine-structure lines are used, together with published optical spectra, to derive the electron temperature of the ionized gas for several ions. A correlation between the electron temperature and the ionization potential is found. Ionic abundances for the observed infrared ions have been derived, and the total neon and sulfur abundances have been determined. These abundances are compared to average LMC abundances of H II regions in order to better understand the chemical evolution of these elements. The nature of the progenitor star is also discussed

THE IRAS MINISURVEY

Before the main IRAS all-sky survey was started, a preliminary survey of 900 deg^2 was carried out. Some results from this "minisurvey" are given here. The completeness of the minisurvey at galactic latitudes lbl = 20°-40° drops sharply at flux densities below 0.4, 0.4, 0.5, and 2.5 Jy at 12, 25, 60, and 100 μm. The corresponding surface densities of point sources brighter than these flux levels are 1.1, 0.4, 0.65, and 1.25 deg^(-2) respectively. Outside the galactic plane, the majority of the sources at 12 and 25 μm are stars, while galaxies make up a significant proportion of 60 μm sources. The 100 μm band is dominated by emission from interstellar dust over much of the minisurvey area