UNUSUAL DUST EMISSION FROM PLANETARY NEBULAE IN THE MAGELLANIC CLOUDS
- Center for Radiophysics and Space Research, Cornell University, 222 Space Sciences Building, Ithaca, NY 14853-6801 (United States)
- Department of Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7 (Canada)
- National Astronomical Observatory of Japan, Osawa 2-21-1, Mikata, Tokyo 181-8588 (Japan)
- Jodrell Bank Centre for Astrophysics, The University of Manchester, Manchester M13 9PL (United Kingdom)
We present a Spitzer Space Telescope spectroscopic study of a sample of 25 planetary nebulae (PNe) in the Magellanic Clouds (MCs). The low-resolution modules are used to analyze the dust features present in the infrared spectra. This study complements a previous work by the same authors where the same sample was analyzed in terms of neon and sulfur abundances. Over half of the objects (14) show emission of polycyclic aromatic hydrocarbons, typical of carbon-rich dust environments. We compare the hydrocarbon emission in our objects to those of Galactic H II regions and PNe, and Large Magellanic Cloud/Small Magellanic Cloud H II regions. Amorphous silicates are seen in just two objects, enforcing the now well known fact that oxygen-rich dust is less common at low metallicities. Besides these common features, some PNe show very unusual dust. Nine objects show a strong silicon carbide feature at 11 {mu}m and 12 of them show magnesium sulfide emission starting at 25 {mu}m. The high percentage of spectra with silicon carbide in the MCs is not common. Two objects show a broadband which may be attributed to hydrogenated amorphous carbon and weak low-excitation atomic lines. It is likely that these nebulae are very young. The spectra of the remaining eight nebulae are dominated by the emission of fine-structure lines with a weak continuum due to thermal emission of dust, although in a few cases the signal-to-noise ratio in the spectra is low, and weak dust features may not have been detected.
- OSTI ID:
- 21333716
- Journal Information:
- Astrophysical Journal, Vol. 699, Issue 2; Other Information: DOI: 10.1088/0004-637X/699/2/1541; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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