We describe spectro-imaging observations of the bright western ridge of the supernova remnant IC443 obtained with the ISOCAM circular variable filter (CVF) on board the Infrared Space Observatory (ISO). The CVF data show that the 5 to 14 µm spectrum is dominated by the pure rotational lines of molecular hydrogen (v = 0–0, S(2) to S(8) transitions). We compare the data to a new time-dependent shock model.

Introduction

The supernova remnant IC443 is a prime example of the interaction of a supernova blast wave with an ambient molecular cloud. On optical plates, IC443 appears as an incomplete shell of filaments (Fig. 1) with a total extent of about 20 arcmin, i.e. ∼ 9pc for an adopted distance of 1,500 pc. The shock generated by the supernova explosion, that occurred (4–13) × 103 years ago, encountered nearby molecular gas which is mainly found along a NW-SE direction across the face of the optical shell. IC443 has been the subject of numerous studies from X-rays, visible, infrared to radio wavelengths (e.g., Mufson et al. 1986 and references therein). Studies of the interaction between the shock and the ambient molecular gas were done by observing molecular hydrogen in the rotational–vibrational transitions (Burton et al. 1988, 1990 – see Fig. 1 – and Richter et al. 1995a), in the pure rotational S(2) transition (Richter et al. 1995b).