Near‐Infrared Imaging and [O i ] Spectroscopy of IC 443 using Two Micron All Sky Survey and Infrared Space Observatory

Abstract

We present near-infrared J (1.25 μm), H (1.65 μm), and Ks (2.17 μm) 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] for 11 positions in the northeast. 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 total luminosity within the 2MASS bands is 1.3×1036 ergs s-1. These data represent the first near-infrared images that are complete in coverage of the remnant. 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 hydrogen recombination lines, Pβ and Br10, should also be present in the broadband images, but probably contribute less than 10% of the J- and H-band fluxes. Strong [O I] (63 μm) lines were detected crossing the northeastern rim, with the strongest line in the northeastern shell where the near-infrared emission shows filamentary structure. In contrast, the southern ridge is dominated by Ks-band light exhibiting a clumped and knotty structure. A two excitation temperature model derived from previous ISO and ground-based observations predicts that H2 lines can explain most of Ks band and at least half of J- and H-band emission. Hence, the prominent broadband color differences arise from physically different mechanisms: atomic fine structure lines along the northeastern rim and molecular rovibrational lines along the southern ridge. Shock models imply a fast J-shock with vs~100 km s-1 and 10