Near-infrared Imaging and [O~I] spectroscopy of IC 443 using 2MASS and ISO

Abstract

We present near-infrared J (1.25um), H (1.65um), and Ks (2.17um) imaging of the entire supernova remnant IC 443 from the Two Micron All Sky Survey (2MASS), and Infrared Space Observatory (ISO) LWS observations of [O I]. Near-infrared emission from IC 443 was detected in all three bands from most of the optically bright parts of the remnant, revealing a shell-like morphology, with bright Ks band emission along the southern ridge and bright J and H along the northeastern rim. The color and morphological structure are very different between the northeastern and southern parts. J and H band emission from the northeast rim is comparably bright and can be explained mostly by [Fe~II] line emission. The southern ridge is dominated by Ks band light exhibiting a clumped and knotty structure. Molecular hydrogen lines can explain most of K$_s$ band and at least half of J and H band emission in the south. Hence, the prominent broad-band color differences arise from physically different mechanisms: atomic fine structure lines along the northeastern rim and molecular ro-vibrational lines along the southern ridge. Shock models imply a fast J-shock with vs~100 km/s and 10<n<10^3 cm^-3 for the northeastern rim and a slow C-shock with vs \~30 km/s and n~10^{4} cm^{-3} for the southern ridge, respectively.