Determine whether compact SO component 1a has a post-shock origin

Determine whether compact SO component 1a emission in the central molecular zone of NGC 253 is compatible with a post-shocked gas origin in addition to warm dense quiescent gas.

Background

The abundance analysis supports SO component 1a as a tracer of warm, dense, quiescent gas. However, the H2CS component 1/SO component 1a ratio is also reproduced by post-shock models independently of the tested shock velocity, pre-shock density, and cosmic-ray ionization rate. The post-shock interpretation therefore remains unresolved.

References

Hence, we cannot exclude that SO$_{\mathrm{comp1a}$ could be also compatible with a post-shocked gas origin.

— 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 “SOcomp1a”