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We present near-infrared (2.5 - 5.0 um) spectra of shocked H2 gas in thesupernova remnant IC 443, obtained with the satellite AKARI. Three shockedclumps-known as B, C, and G-and one background region were observed, and onlyH2 emission lines were detected. Except the clump B, the extinctioncorrectedlevel population shows the ortho-to-para ratio of ~ 3.0. From the levelpopulation of the clumps C and G-both AKARI's only and the one extended withprevious mid-infrared observations-we found that the v = 0 levels are morepopulated than the v > 0 levels at a fixed level energy, which cannot bereproduced by any combination of H2 gas in Local Thermodynamic Equilibrium. Thepopulations are described by the two-density power-law thermal admixture model,revised to include the collisions with H atoms. We attributed the lower(n(H2)=10^(2.8-3.8) cm-3) and higher (n(H2)=10^(5.4-5.8) cm-3) density gases tothe shocked H2 gas behind C-type and J-type shocks, respectively, based onseveral arguments including the obtained high H I abundance n(H I)/n(H2)=0.01.Under the hierarchical picture of molecular clouds, the C-type and J-typeshocks likely propagate into "clumps" and "clouds" (interclump media),respectively. The power-law index b of 1.6 and 3.5, mainly determined by thelower density gas, is attributed to the shock-velocity diversity, which may bea natural result during shock-cloud interactions. According to our results, H2v = 1 - 0 S(1) emission is mainly from J-shocks propagating into interclumpmedia. The H2 emission was also detected at the background region, and thisdiffuse H2 emission may originate from collisional process in addition to theultraviolet photon pumping.

AKARI Near-infrared Spectral Observations of Shocked H2 Gas of the Supernova Remnant IC 443