SPITZER CHARACTERIZATION OF DUST IN THE IONIZED MEDIUM OF THE LARGE MAGELLANIC CLOUD
- Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)
- Institut d'Astrophysique Spatiale, 91405 Orsay (France)
- Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya 464-8602 (Japan)
- Department of Physical Science, Osaka Prefecture University, Gakuen 1-1, Sakai, Osaka 599-8531 (Japan)
A systematic investigation of dust emission associated with ionized gas has so far been performed only in our Galaxy and for wavelengths longer than 60 {mu}m. Newly available Spitzer data now offer the opportunity to carry out a similar analysis in the Large Magellanic Cloud (LMC). By cross-correlating Spitzer Surveying the Agents of a Galaxy's Evolution (SAGE) data with the Australia Telescope Compact Array/Parkes H I 21 cm data, the NANTEN {sup 12}CO (J = 1-0) data, and both the Southern H-Alpha Sky Survey Atlas H{alpha} and the Parkes 6 cm data, we investigate the physical properties of dust associated with the different phases of the gas (atomic, molecular, and ionized). In particular, we study the presence and nature of dust from 3.6 to 160 {mu}m and for various regimes of ionized gas, spanning emission measures from {approx}1 pc cm{sup -6} (diffuse component) to {approx}10{sup 3}pc cm{sup -6} (H II regions). Using a dust emission model and testing our results with several radiation field spectra, we show that dust in ionized gas is warmer than dust associated with other phases (atomic and molecular). We also find a decrease of the polycyclic aromatic hydrocarbon (PAH) relative abundance with respect to big grains, as well as an increase of the near-infrared (NIR) continuum. These three results (i.e., warmer temperature, decrease of PAH abundance, and increase of the NIR continuum) are found consistently for all regimes of ionized gas. On the contrary, the molecular phase appears to provide favorable conditions for the survival of PAHs. Furthermore, the very small grain relative abundance tends to increase in the ionized phase, especially in bright H II regions. Last but not least, our analysis shows that the emissivity of dust associated with ionized gas is lower in the LMC than in our Galaxy and that this difference is not accounted for by the lower metallicity of the LMC.
- OSTI ID:
- 21576575
- Journal Information:
- Astrophysical Journal, Vol. 735, Issue 1; Other Information: DOI: 10.1088/0004-637X/735/1/6; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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