Distinguish shock and post-shock origins of compact OCS and H2CS emission

Determine whether compact OCS component 1 and H2CS component 1 emission in the central molecular zone of NGC 253 originates in shocked gas or post-shocked gas.

Background

The compact OCS component 1 and H2CS component 1 abundance ratio is consistent with both shock and post-shock chemical models, largely because the observed ratio spans several orders of magnitude. Although the modelling supports the interpretation that the two species are associated with shocked or post-shocked material, it does not identify which of these two evolutionary phases is responsible.

References

Overall, the models seem to support the observational conclusions (OCS probe shocks while \ce{H2CS} probes post-shocks; \citetalias{bouvier2024}), although we cannot distinguish between shock or post-shock origins.

— Sulphur within the extreme environment of the central molecular zone of NGC 253: a chemical modelling approach  (2609.01162 - Bouvier et al., 1 Sep 2026) in Section 4.2.3, paragraph “OCScomp1 and H2CScomp1”