Explaining Major Sources of Sulfur-Bearing Molecules in the Interstellar Medium

Abstract

Despite the lower abundance of sulfur, it owns a pivotal part in the interstellar chemistry. Sulfur-bearing molecules are utilized to investigate the physical property and determine the age of a star-forming region. The major sulfur reservoir of the Interstellar medium (ISM) is a long-standing mystery. In the diffuse region, the abundance of sulfur seemed to be cosmic but in the dense cloud, it significantly deviates from the cosmic sulfur abundance (∼ 10⁻⁵). In last few decades, various simple sulfur-bearing molecules were observed in different regions of the ISM or circumstellar shells. Among the complex sulfur yielding species, methanethiol (CH ₃SH) has been firmly detected in the ISM. Investigations are going on for the discovery of the more complex sulfur species. Tentative detection of ethanethiol (C ₂H ₅SH) in the ISM has been recently reported. Based on this trend, we investigated the formation of higher order alcohols and their analogous sulfur species. Quantum chemical calculation has been employed to find out the most stable conformer of higher order alcohols and their sulfur analogues and their formation pathways under interstellar conditions. Kinetic information obtained from the quantum chemical calculations can be used in gas-grain chemical modeling to study the chemical evolution of these alcohols and thiols.