The Role of Radiolysis in the Modelling of C${}_2$H${}_4$O${}_2$ Isomers and Dimethyl Ether in Cold Dark Clouds

Abstract

Complex organic molecules (COMs) have been detected in a variety of interstellar sources. The abundances of these COMs in warming sources can be explained by syntheses linked to increasing temperatures and densities, allowing quasi-thermal chemical reactions to occur rapidly enough to produce observable amounts of COMs, both in the gas phase, and upon dust grain ice mantles. The COMs produced on grains then become gaseous as the temperature increases sufficiently to allow their thermal desorption. The recent observation of gaseous COMs in cold sources has not been fully explained by these gas-phase and dust grain production routes. Radiolysis chemistry is a possible non-thermal method of producing COMs in cold dark clouds. This new method greatly increases the modeled abundance of selected COMs upon the ice surface and within the ice mantle due to excitation and ionization events from cosmic ray bombardment. We examine the effect of radiolysis on three C${}_2$H${}_4$O${}_2$ isomers -- methyl formate (HCOOCH${}_3$), glycolaldehyde (HCOCH${}_2$OH), and acetic acid (CH${}_3$COOH) -- and a chemically similar molecule, dimethyl ether (CH${}_3$OCH${}_3$), in cold dark clouds. We then compare our modelled gaseous abundances with observed abundances in TMC-1, L1689B, and B1-b.

12 pages, 6 Figures, 5 tables, 33 numbered equations

References in corpus (18)

• Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model
• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• Polycylcic Aromatic Hydrocarbons (PAH's) in dense cloud chemistry
• Formation of complex organic molecules in cold objects: the role of gas phase reactions
• The origin of complex organic molecules in prestellar cores
• The Spatial Distribution of Complex Organic Molecules in the L1544 Pre-stellar Core
• Experimental evidence for Glycolaldehyde and Ethylene Glycol formation by surface hydrogenation of CO molecules under dense molecular cloud conditions
• Modeling Complex Organic Molecules in dense regions: Eley-Rideal and complex induced reaction
• Formation of Complex Organic Molecules in Cold Interstellar Environments through non-diffusive grain-surface and ice-mantle chemistry
• Efficient Production of S${}_8$ in Interstellar Ices: The effects of cosmic ray-driven radiation chemistry and non-diffusive bulk reactions
• Chemical complexity induced by efficient ice evaporation in the Barnard 5 molecular cloud
• The Case of H${}_2$C${}_3$O Isomers, Revisited: Solving the Mystery of the Missing Propadienone
• On Simulating the Proton-Irradiation of O${}_2$ and H${}_2$O Ices Using Astrochemical-type Models, with Implications for Bulk Reactivity
• Isomers in Interstellar Environments (I): The Case of Z- and E-Cyanomethanimine
• ALMA Observations of the Spatial Distribution of three C${}_2$H${}_4$O${}_2$ Isomers towards Sgr B2(N)
• Chemical significance of different temperature regimes for cosmic-ray-induced heating of whole interstellar grains

Cited by in corpus (1)

• Carbon-Chain Chemistry vs. Complex-Organic-Molecule Chemistry in Envelopes around Three Low-Mass Young Stellar Objects in the Perseus Region