Observations of the Far-Infrared Emission Lines of OI and CII in Planetary Nebulae

Abstract

We have made observations of the far-infrared, fine structure emission lines [01] 63 μm, [01] 145 μm, and [CII] 158 μm in the proto-planetary nebulae AFGL 2688 and AFGL 618, and the classical planetary nebulae IC 418 and NGC 7027. The observations were made with the UC Berkeley tandem Fabry-Perot spectrometer aboard the Kuiper Airborne Observatory in October, 1983. Apertures of 30″ (63 μm) and 45″ (145 μm and 158 μm) were used. We detected all three lines in NGC 7027, but obtained only upper limits to the 63 μm emission from the other three nebulae and the 158 μm emission from AFGL 618. The line fluxes in NGC 7027 are: [OI] 63 μm, 3.2 ± 1.0 × 10^–17 W cm^-2; [OI] 145 μm, 1.2 ± 0.4 × 10–18 W cm^-2; [CII] 158 μm, 3.4 ± 1.0 × 10^–18 W cm^-2. The [01] 63 μm line has been detected previously in NGC 7027 by Melnick et al. (1981) but these observations represent the first detections of the [OI] 145 μm and [CII] 158 μm lines in a planetary nebula.

NAS/NRC Research Associate