DISCOVERY AND ANALYSIS OF 21 {mu}m FEATURE SOURCES IN THE MAGELLANIC CLOUDS
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Department of Physics and Astronomy, Valparaiso University, Valparaiso, IN 46383 (United States)
- Department of Physics and Astronomy, UCL-Institute of Origins, University College London, Gower Street, London WC1E 6BT (United Kingdom)
- Institut d Astrophysique Spatiale, CNRS/Universite Paris-Sud 11, 91405, Orsay (France)
- N. Copernicus Astronomical Center, Rabianska 8, 87-100 Torun (Poland)
- Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)
- Air Force Research Laboratory, AFRL/RVBYB, 29 Randolph Road, Hanscom AFB, MA 01731 (United States)
- Astrophysics Group, Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG (United Kingdom)
- Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)
- Jet Propulsion Laboratory, MS 183-900, California Institute of Technology, Pasadena, CA 91109 (United States)
- Astronomy Department, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States)
- Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22903 (United States)
- Department of Physics and Astronomy, Iowa State University, A313E Zaffarano, Ames, IA 50011 (United States)
Spitzer Space Telescope mid-infrared spectroscopy has been obtained for 15 carbon-rich protoplanetary nebulae (PPNe) in the Large Magellanic Cloud (LMC) and for two other such stars in the Small Magellanic Cloud (SMC). Of these 17 PPNe, the unidentified 21 {mu}m feature is strong in 7 spectra, weak in 2 spectra, and very weak or questionable in 4 spectra. Two of the four spectra without the 21 {mu}m feature have a very strong feature near 11 {mu}m, similar to a feature observed in some carbon-rich planetary nebulae (PNe) in the LMC. We attribute this feature to unusual SiC dust, although the feature-to-continuum ratio is much larger than for SiC features in Galactic or Magellanic Cloud carbon star spectra. The remaining two objects show typical carbon-rich PPNe spectra with no 21 {mu}m features. One of the LMC objects that lacks the 21 {mu}m feature and one SMC object with a questionable 21 {mu}m detection may have mixed dust chemistries based upon their spectral similarity to Galactic [WC] PNe. The 13 objects that either definitely or may show the 21 {mu}m feature have distinct dust shell properties compared to the Galactic 21 {mu}m objects-the 21 {mu}m features are weaker, the estimated dust temperatures are significantly higher, the unidentified infrared (UIR) bands are stronger, and the UIRs show more structure. Four of the 21 {mu}m objects appear to show normal SiC emission features in their spectra. Many of the PPNe show strong 30 {mu}m features, although this feature carries less of the total mid-infrared emission than is normally the case for the Galactic 21 {mu}m PPNe. The LMC objects are in the LMC halo rather than in the LMC bar. The estimated luminosities of these PPNe vary from 4700 to 12,500 L{sub sun}.
- OSTI ID:
- 21578374
- Journal Information:
- Astrophysical Journal, Vol. 735, Issue 2; Other Information: DOI: 10.1088/0004-637X/735/2/127; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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