DISCOVERY AND ANALYSIS OF 21 {mu}m FEATURE SOURCES IN THE MAGELLANIC CLOUDS

Journal Article · Sun Jul 10 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/735/2/127· OSTI ID:21578374

Volk, Kevin; Meixner, Margaret; Gordon, Karl D ^[1]; Hrivnak, Bruce J ^[2]; Matsuura, Mikako ^[3]; Bernard-Salas, Jeronimo ^[4]; Szczerba, Ryszard ^[5]; Sloan, G C ^[6]; Kraemer, Kathleen E ^[7]; Van Loon, Jacco Th ^[8]; Kemper, F; Woods, Paul M; Zijlstra, Albert A ^[9]; Sahai, Raghvendra ^[10]; Gruendl, Robert A ^[11]; Indebetouw, Remy ^[12]; Marengo, Massimo ^[13]

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1. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
2. Department of Physics and Astronomy, Valparaiso University, Valparaiso, IN 46383 (United States)
3. Department of Physics and Astronomy, UCL-Institute of Origins, University College London, Gower Street, London WC1E 6BT (United Kingdom)
4. Institut d Astrophysique Spatiale, CNRS/Universite Paris-Sud 11, 91405, Orsay (France)
5. N. Copernicus Astronomical Center, Rabianska 8, 87-100 Torun (Poland)
6. Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)
7. Air Force Research Laboratory, AFRL/RVBYB, 29 Randolph Road, Hanscom AFB, MA 01731 (United States)
8. Astrophysics Group, Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG (United Kingdom)
9. Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)
10. Jet Propulsion Laboratory, MS 183-900, California Institute of Technology, Pasadena, CA 91109 (United States)
11. Astronomy Department, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States)
12. Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22903 (United States)
13. 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, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 735; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION SPECTROSCOPY
CARBIDES
CARBON COMPOUNDS
CARBON STARS
DUSTS
EMISSION
EVOLUTION
GALAXIES
INFRARED SPECTRA
MAGELLANIC CLOUDS
MAIN SEQUENCE STARS
NEBULAE
PLANETARY NEBULAE
PROTOPLANETS
SILICON CARBIDES
SILICON COMPOUNDS
SPECTRA
SPECTROSCOPY
STAR EVOLUTION
STARS