Carbon Monoxide in the Cassiopeia A Supernova Remnant

TL;DR

This paper reports the detection of near-infrared CO emission in Cassiopeia A, indicating ongoing molecule formation and limited mixing in the supernova ejecta, with implications for astrochemistry over centuries.

Contribution

First detection of near-infrared CO emission in Cassiopeia A, providing insights into molecule formation and ejecta mixing in supernova remnants.

Findings

CO knots are present within the ejecta-rich reverse shock.

Approximately 30 times less CO in Cas A compared to SN 1987A.

Molecule formation may continue for at least 300 years after explosion.

Abstract

We report the likely detection of near-infrared 2.29 $\mu$m first overtone Carbon Monoxide (CO) emission from the young supernova 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 $\sim$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 ~300 years after the initial explosion.