A Unified Microscopic-Macroscopic Monte Carlo Simulation of Gas-Grain Chemistry in Cold Dense Interstellar Clouds

Abstract

For the first time, we report a unified microscopic-macroscopic Monte Carlo simulation of gas-grain chemistry in cold interstellar clouds in which both the gas-phase and the grain surface chemistry are simulated by a stochastic technique. The surface chemistry is simulated with a microscopic Monte Carlo method in which the chemistry occurs on an initially flat surface. The surface chemical network consists of 29 reactions initiated by the accreting species H, O, C, and CO. Four different models are run with diverse but homogeneous physical conditions including temperature, gas density, and diffusion-barrier-to-desorption energy ratio. As time increases, icy interstellar mantles begin to grow. Our approach allows us to determine the morphology of the ice, layer by layer, as a function of time, and to ascertain the environment or environments for individual molecules. Our calculated abundances can be compared with observations of ices and gas-phase species, as well as the results of other models.

ApJ accepted. 37 pages, 9 figures

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• Interstellar Simulations Using A Unified Microscopic-Macroscopic Monte Carlo Model with a full Gas-Grain Network including Bulk Diffusion in Ice Mantles
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• Laboratory and Computational Studies of Interstellar Ices
• A New and Simple Approach to Determine the Abundance of Hydrogen Molecules on Interstellar Ice Mantles
• Interactions of adsorbed CO${}_2$ on water ice at low temperatures
• VLT/ISAAC infrared spectroscopy of embedded high-mass YSOs in the Large Magellanic Cloud: Methanol and the 3.47 micron band
• Adsorption of H${}_2$ on Amorphous Solid Water Studied with Molecular Dynamics Simulations
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• Quantifying the chemical desorption of H${}_2$S and PH${}_3$ from amorphous water ice surfaces
• The effect of selective desorption mechanisms during interstellar ice formation
• H2 chemistry in interstellar ices: the case of CO ice hydrogenation in UV irradiated CO:H2 ice mixtures
• Alcohols on the rocks: solid-state formation in a H3CCCH + OH cocktail under dark cloud conditions
• Chemical modeling of the complex organic molecules in the extended region around Sagittarius B2
• Effects of turbulent dust grain motion to interstellar chemistry
• Cosmic-ray-induced dissociation and reactions in warm interstellar ices
• Effect of stochastic grain heating on cold dense clouds chemistry
• Modelling carbon-chain species formation in lukewarm corinos with new multi-phase models
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• Effect of surface H${}_2$ on molecular hydrogen formation on interstellar grains
• MAGellanic Outflow and chemistry Survey (MAGOS): Hot cores in the LMC
• Experimental investigation of O2 diffusion and entrapment in interstellar amorphous solid water (ASW)