Formation and destruction of SiS in space

Abstract

The presence of SiS in space seems to be restricted to a few selected types of astronomical environments. It is long known to be present in circumstellar envelopes around evolved stars and it has also been detected in a handful of star-forming regions with evidence of outflows, like Sgr\,B2, Orion\,KL and more recently L1157-B1. The kinetics of reactions involving SiS is very poorly known and here we revisit the chemistry of SiS in space by studying some potentially important reactions of formation and destruction of this molecule. We calculated {\it ab initio} potential energy surfaces of the SiOS system and computed rate coefficients in the temperature range 50-2500 K for the reaction of destruction of SiS, in collisions with atomic O, and of its formation, through the reaction between Si and SO. We find that both reactions are rapid, with rate coefficients of a few times 10${}^{-10}$ cm${}^3$ s${}^{-1}$, almost independent of temperature. In the reaction between Si and SO, SiO production is 5-7 times more efficient than SiS formation. The reaction of SiS with O atoms can play an important role in destroying SiS in envelopes around evolved stars. We built a simple chemical model of a postshock gas to study the chemistry of SiS in protostellar outflows and we found that SiS forms with a lower abundance and later than SiO, that SiS is efficiently destroyed through reaction with O, and that the main SiS-forming reactions are Si + SO and Si + SO${}_2$.

arXiv commentAccepted for publication in AstroPhys. J. (June 2018)

References in corpus (10)

• SiO line emission from C-type shock waves : interstellar jets and outflows
• Molecular abundances in the inner layers of IRC +10216
• A line confusion limited millimeter survey of Orion KL. II: Silicon-bearing species
• The growth of carbon chains in IRC+10216 mapped with ALMA
• Photochemistry in the inner layers of clumpy circumstellar envelopes: formation of water in C-rich objects and of C-bearing molecules in O-rich objects
• The abundance of SiS in circumstellar envelopes around AGB stars
• Silicon-bearing molecules in the shock L1157-B1: first detection of SiS around a Sun-like protostar
• Si-bearing molecules towards IRC+10216: ALMA unveils the molecular envelope of CWLeo
• High-J v=0 SiS Maser Emission in IRC+10216: A New Case of Infrared Overlaps
• The abundance of 28Si32S, 29Si32S, 28Si34S, and 30Si32S in the inner layers of the envelope of IRC+10216

Cited by in corpus (11)

• SO and SiS Emission Tracing an Embedded Planet and Compact ${}^{12}$CO and ${}^{13}$CO Counterparts in the HD 169142 Disk
• The first detection of SiC${}_2$ in the interstellar medium
• Silicon and hydrogen chemistry under laboratory conditions mimicking the atmosphere of evolved stars
• SiS formation in the interstellar medium through Si+SH gas phase reactions
• Observations of Orion Source I Disk and Outflow Interface
• First detection of silicon-bearing molecules in $\eta$ Car
• Structures and Properties of Known and Postulated Interstellar Cations
• New SiS destruction and formation routes via neutral-neutral reactions and their fundamental role in interstellar clouds at low and high metallicity values
• The S${}^{+}$(${}^4$S) + SiH${}_2$(${}^1$A${}_1$) Reaction: Toward the Synthesis of Interstellar SiS
• IRC+10216 mass loss properties through the study of $\lambda$3mm emission: Large spatial scale distribution of SiO, SiS, and CS
• The Si+SO${}_2$ collision and an extended network of neutral-neutral reactions between silicon and sulphur bearing species