Near-infrared [Fe II] and H 2 Line Mapping of the Supernova Remnant IC 443 with the IRSF/SIRIUS

Abstract

We investigate properties of the interstellar medium (ISM) interacting with shocks around the Galactic supernova remnant IC 443, using the results of near-infrared [Fe ii ] and H 2 line mapping with the InfraRed Survey Facility/Simultaneous Infrared Imager for Unbiased Survey. In the present study, we newly performed H 2 1–0 S(1) and 2–1 S(1) line mapping with the narrowband filters tuned for these lines, covering the entire remnant ( 30 ′ × 35 ′ ). Combined with an [Fe ii ] line map, our result shows that the H 2 line emission is significantly detected in the southern region, while the [Fe ii ] 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 H 2 line emission is relatively strong compared to the [Fe ii ] line emission in the southwestern region, where TeV γ -ray emission is detected. As the strong H 2 line emission indicates the dominance of the dense ISM, this result supports the scenario that the γ -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 H 2 and [Fe ii ] 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 IC 443 may assist cosmic-ray protons to efficiently interact with large amounts of the ISM protons.