Toward the detection of the sulphur reservoir(s) in the JWST era ?

The abundances of sulphur species in the gas-phase observed in star-forming regions represent only a tiny fraction (<1 %) of the cosmic sulphur abundance. The majority of sulphur in the interstellar medium (ISM) is expected to be in solid form, either in an ice mantle or in (semi-)refractory form. The search for solid-phase sulphur in the ISM has not yet been successful: only OCS has been unambiguously detected, with attempts to detect H2S and SO2. The column density estimates for these two species only represent <5 % of the cosmic abundance of sulphur. This leaves around 90% of this species hidden in a form that has not yet been detected. Current chemical models have difficulty implementing sulphur chemistry with other elements, despite recent efforts to improve the prescriptions on chemical networks. Models predict that a large fraction of the volatile sulphur species in dense cores are found in ice mantles. Recent observations also suggest that sulphur depletion and composition of sulphur species in the ices are strongly affected by the dynamics and chemical history of the cloud. We will present a tool for generating synthetic ice spectra, based on the JWST instrumentation, based on a simple approximation of laboratory spectra to predict NIRSpec and MIRI observations. We study the feasibility of detecting sulphur species (in particular H2S, CS2, SO2 and S8) in ice and to understand which physico-chemical environments would enable such reservoirs to be obtained in ice.