2024ApJ...977..149R

Supernova shocks into dense molecular cores in IC 443 (clumps B, C, and G) and 3C 391 were observed using the Stratospheric Observatory for Infrared Astronomy and complemented by archival data from the Herschel Space Observatory. The pure rotational transitions 0-0 S(1) and S(5) of H₂, and the ground-state 1₁₀-1₀₁ transition of H₂O, are all broadened, arising from molecules that survive the passage of the shock front. Theoretical models from the Paris-Durham shock code were analyzed to generate velocity profiles that approximately match the observations. The observations can be fit with two shock conditions, which approximate the range of densities in the preshock molecular cloud. The width and brightness of the S(5) lines require shocks into gas with a density of order 2000 cm^–3, into which the IC 443 blast wave drives shocks with speed 60 km s^–1. The brightness and narrower width of the S(1) lines requires different shocks, into gas with density of order 10⁵ cm^–3, with shock speeds of 10 km s^–1. The H₂O velocity distribution is also consistent with these shocks. The existence of shocks into dense gas shows that the bright shocked clumps in IC 443 were prestellar cores. It is unlikely that they will form stars soon after the passage of the shock front, given the input of kinetic and thermal energy from the shocks.