Modeling Complex Organic Molecules’ Formation in Cold Cores: Multiphase Models with Nonthermal Mechanisms

Abstract

In recent years, a significant number of oxygen-bearing complex organic molecules (COMs) have been detected in the gas phase of cold dark clouds such as TMC-1. The formation of these COMs cannot be explained by diffusive mechanisms on grains and gas-phase reactions. This study investigates the formation of oxygen-bearing COMs in cold dark clouds using multiphase gas–grain models that incorporate cosmic ray-induced nondiffusive radiation chemistry and nonthermal sputtering desorption mechanisms. Additionally, we present the effects of varying elemental C/O ratio and different sputtering rates. We utilized an accelerated Gillespie algorithm, based on the regular Gillespie algorithm. The results of our models for dimethyl ether (CH _3 OCH _3 ), methyl formate (HCOOCH _3 ), acetaldehyde (CH _3 CHO), ethanol (C _2 H _5 OH), and methanol (CH _3 OH) show reasonable agreement with observations toward TMC-1, within a factor of 3. Out of the 94 species compared with observations, 63 show agreement within 1 order of magnitude, accounting for 67.02%. Overall inclusion of nonthermal mechanisms in multiphase models shows notable improvement of modeling on oxygen-bearing COMs in the interstellar medium.

Keywords

• Astrochemistry
• Interstellar medium