Paradis, Déborah and Paladini, Roberta and Noriega-Crespo, Alberto and Lagache, Guilaine and Kawamura, Akiko and Onishi, Toshikazu and Fukui, Yasuo (2011) Spitzer Characterization of Dust in the Ionized Medium of the Large Magellanic Cloud. Astrophysical Journal, 735 (1). Art. No. 6. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20110705-101507325
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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 μm. 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 ^(12)CO (J = 1-0) data, and both the Southern H-Alpha Sky Survey Atlas Hα 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 μm and for various regimes of ionized gas, spanning emission measures from ~1 pc cm^(–6) (diffuse component) to ~10^3 pc cm^(–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.
|Additional Information:||© 2011 American Astronomical Society. Received 2010 December 17; accepted 2011 April 4; published 2011 June 8. We thank the referee for useful comments, which helped to improve the content of the paper. We also thank M. Filipovic and A. Hughes for helpful discussions on the Parkes radio data and on the derivation of the thermal fraction. We acknowledge the use of the DustEM package. The NANTEN project is based on a mutual agreement between Nagoya University and the Carnegie Institution of Washington (CIW). This work is financially supported in part by a Grand-in-Aid for Scientific Research from JSPS (Nos. 22244014 and 30377931).|
|Subject Keywords:||dust, extinction; Hii regions; Magellanic Clouds|
|Classification Code:||PACS: 98.56.Si; 98.58.Hf; 98.58.Ca; 95.30.Ky; 95.85.Jq; 98.58.Kh|
|Official Citation:||Spitzer Characterization of Dust in the Ionized Medium of the Large Magellanic Cloud Déborah Paradis et al. 2011 ApJ 735 6|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||05 Jul 2011 18:11|
|Last Modified:||26 Dec 2012 13:22|
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