The sulphur depletion problem in molecular clouds: The H₂S case

Observatorio Astronómico Nacional, IGN-CNIG, Calle Alfonso XII, 3-5, 28014 Madrid, Spain

Published online: 7 September 2022

Abstract

Sulphur is one of the most abundant elements in the Universe and plays a crucial role in biological systems. However, sulphuretted molecules in the ISM are not as abundant as expected and there is no clear answer of where the missing Sulphur is yet. To shed light onto this open question, we focus our attention on the chemistry of H₂S, thought to be an important reservoir of Sulphur and formed mainly by grain-phase reactions. To understand the formation of H₂S, the growth of ices, and the chemical desorption process, we study the CO, CH₃OH, N₂H⁺, and H₂S abundances towards Barnard 1b, a Sulphur-rich cloud hosting a first Larson core. We look for correlations between gas-phase abundances of H₂S and CH₃OH that better constrain the location of the CO snowline in dark cores. Finally, this provides additional data to benchmark models for a deeper insight on the chemical desorption process and its efficiency.