Complex molecule formation in grain mantles

Abstract

Context. Complex molecules such as ethanol and dimethyl ether have been observed in a number of hot molecular cores and hot corinos. Attempts to model the molecular formation process using gas phase only models have so far been unsuccessful. Aims. To demonstrate that grain surface processing is a viable mechanism for complex molecule formation in these environments. Methods. A variable environment parameter computer model has been constructed which includes both gas and surface chemistry. This is used to investigate a variety of cloud collapse scenarios.Results. Comparison between model results and observation shows that by combining grain surface processing with gas phase chemistry complex molecules can be produced in observed abundances in a number of core and corino scenarios. Differences in abundances are due to the initial atomic and molecular composition of the core/corino and varying collapse timescales. Conclusions. Grain surface processing, combined with variation of physical conditions, can be regarded as a viable method for the formation of complex molecules in the environment found in the vicinity of a hot core/corino and produce abundances comparable to those observed.

Full SED fitting with the KOSMA-τPDR code

“…Many important physical and chemical processes require a good knowledge of the properties of interstellar dust grains (Abel et al 2008). Chemical reactions on the surface of dust grains appear to be the only efficient formation route for a number of important astrochemical species (Garrod et al 2008;Hall & Millar 2010). The specifics of their reaction kinematics depend to a large degree on the material properties and the structure of the dust grains.…”