CARBON MONOXIDE IN THE CASSIOPEIA A SUPERNOVA REMNANT

We report the likely detection of near-infrared 2.29 mu m first overtone carbon monoxide (CO) emission from the young supernova (SN) remnant Cassiopeia A (Cas A). The continuum-subtracted CO filter map reveals CO knots within the ejecta-rich reverse shock. We compare the first overtone CO emission with that found in the well studied supernova SN 1987A and find similar to 30 times less CO in Cas A. The presence of CO suggests that molecule mixing is small in the SN ejecta and that astrochemical processes and molecule formation may continue at least similar to 300 yr after the initial explosion.