Atomic carbon emission from shocked and preshocked gas in the IC 443 supernova remnant

Abstract

We have obtained maps of C I (³ P ₁→³ P ₀) emission at 492 GHz in the Supernova Remnant IC 443, concentrating on clump G. Broad-line shocked CI emission (≈10 kms⁻¹ FWHM) with spatial distribution similar to that of ¹²CO is observed. Also, very interestingly, we see a narrow-line (≈1 kms⁻¹ FWHM) component of C I emission that corresponds to no observed ¹²CO emission and its distribution is very different from that of the shocked component, apparently lying upstream from the shock front. Both wide and narrow components are also weakly visible in our ¹³CO(2→1) map. The inferred ratio of C I to CO in the shocked component is >0.5 and in the narrow-line component is >2, rather than the usual value of about 0.1. We speculate that this predominantly atomic region may mark the radiative precursor of the shock.