Infrared spectra of IC 418 and NGC 6572.
Abstract
Spectrophotometric observations from 2 to 4 and 8 to 13 microns of NGC 6572 and from 4 to 13 microns of IC 418 are reported. Also reported are observations of the size of IC 418 in the optical and at 1.65 and 2.2 microns. Both planetary nebulae emit more radiation than expected from recombination at wavelengths longer than -4 microns; this radiation is attributed to heated dust. The spectra show a plateau from 10.5 to 13 microns, and this peak is tentatively attributed to emission from large silicon carbide particles. Fine-structure emission lines are also discussed; the presence of (forbidden Ar III) but not (forbidden Ne II) in NGC 6572 suggests that ions having the same ionization potential can nevertheless have different fractional abundances.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1979
- DOI:
- 10.1086/157521
- Bibcode:
- 1979ApJ...234..496W
- Keywords:
-
- Infrared Spectra;
- Planetary Nebulae;
- Radiative Recombination;
- Spectrophotometry;
- Emission Spectra;
- Fine Structure;
- Ionization Potentials;
- Silicon Carbides;
- Astrophysics;
- Emission Lines:Planetary Nebulae;
- Infrared Spectra:Planetary Nebulae