AKARI NEAR-INFRARED SPECTRAL OBSERVATIONS OF SHOCKED H{sub 2} GAS OF THE SUPERNOVA REMNANT IC 443
- Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-gu, Daejeon 305-348 (Korea, Republic of)
- Department of Physics and Astronomy, FPRD, Seoul National University, 599 Gwanangno, Gwanak-gu, Seoul 151-747 (Korea, Republic of)
- Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada)
We present near-infrared (2.5-5.0 {mu}m) spectra of shocked H{sub 2} gas in the supernova remnant IC 443, obtained with the satellite AKARI. Three shocked clumps-known as B, C, and G-and one background region were observed, and only H{sub 2} emission lines were detected. Except in clump B, the extinction-corrected level population shows the ortho-to-para ratio of {approx}3.0. From the level populations of clumps C and G-both the one obtained with AKARI and the one extended with previous mid-infrared observations-we found that the {upsilon} = 0 levels are more populated than the {upsilon}>0 levels at a fixed level energy, which cannot be reproduced by any combination of H{sub 2} gas in local thermodynamic equilibrium. The populations are described by the two-density power-law thermal admixture model, revised to include the collisions with H atoms. We attributed the lower (n(H{sub 2})=10{sup 2.8}-10{sup 3.8} cm{sup -3}) and higher (n(H{sub 2})=10{sup 5.4}-10{sup 5.8} cm{sup -3}) density gases to the shocked H{sub 2} gas behind C-type and J-type shocks, respectively, based on several arguments including the obtained high H I abundance n(H I)/n(H{sub 2}) = 0.01. Under the hierarchical picture of molecular clouds, the C-type and J-type shocks likely propagate into 'clumps' and 'clouds' (interclump media), respectively. The power-law index b of 1.6 and 3.5, mainly determined by the lower density gas, is attributed to the shock-velocity diversity, which may be a natural result during shock-cloud interactions. According to our results, H{sub 2} {upsilon} = 1 {yields} 0 S(1) emission is mainly from J shocks propagating into interclump media. The H{sub 2} emission was also detected at the background region, and this diffuse H{sub 2} emission may originate from the collisional process in addition to ultraviolet photon pumping.
- OSTI ID:
- 21576841
- Journal Information:
- Astrophysical Journal, Vol. 732, Issue 2; Other Information: DOI: 10.1088/0004-637X/732/2/124; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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