Shocked molecular hydrogen in the supernova remnant IC 443.

Emission from the υ = 1-0 S(1) line of molecular hydrogen has been mapped over a section of the supernova remnant IC 443. The emission originates in a sinuous ridge where the expanding shell of the SNR is interacting with a molecular cloud. The relative intensities of the 1-0 S(1), 1-0 S(0) and 2-1 S(1) lines at 2.1 - 2.2 μm were measured and found to be characteristic of shock-excitation of the gas. The ridge shows bright spots which are possibly density enhancements in the molecular cloud. The total luminosity of the molecular hydrogen lines in the mapped region is estimated to be about 1000 L_sun;, making IC 443 one of the most luminous galactic molecular hydrogen sources yet detected. A model for IC 443 is presented involving the expansion of the SN shock-wave inside the remains of a molecular disc left over from the process of formation of the star which exploded.