  We investigate properties of the interstellar medium (ISM) interacting with
shocks around the Galactic supernova remnant IC443, using the results of
near-infrared [FeII] and H2 line mapping with the IRSF/SIRIUS. In the present
study, we newly performed H2 1-0 S(1) and 2-1 S(1) line mapping with the
narrow-band filters tuned for these lines, covering the entire remnant
(30'x35'). Combined with an [FeII] line map, our result shows that the H2 line
emission is significantly detected in the southern region, while the [FeII]
line emission is detected all over the remnant, suggesting that slow and fast
shocks propagate through the southern region and the entire remnant,
respectively. In particular, the H2 line emission is relatively strong compared
to the [FeII] line emission in the southwestern region, where TeV gamma-ray
emission is detected. As the strong H2 line emission indicates the dominance of
the dense ISM, this result supports the scenario that the gamma-ray emission is
likely to be produced through a heavy interaction between cosmic-ray protons
and the dense ISM in the southwestern shell. We also find that the H2 and
[FeII] line emissions show an anti-correlated spatial distribution in the same
region, suggesting the presence of the clumpy ISM. Such a clumpy morphology of
the ISM around IC443 may assist cosmic-ray protons to efficiently interact with
large amounts of the ISM protons.
