Effects of turbulent dust grain motion to interstellar chemistry

Abstract

Theoretical studies have revealed that dust grains are usually moving fast through the turbulent interstellar gas, which could have significant effects upon interstellar chemistry by modifying grain accretion. This effect is investigated in this work on the basis of numerical gas-grain chemical modeling. Major features of the grain motion effect in the typical environment of dark clouds (DC) can be summarised as follows: 1) decrease of gas-phase (both neutral and ionic) abundances and increase of surface abundances by up to 2-3 orders of magnitude; 2) shifts of the existing chemical jumps to earlier evolution ages for gas-phase species and to later ages for surface species by factors of about ten; 3) a few exceptional cases in which some species turn out to be insensitive to this effect and some other species can show opposite behaviors too. These effects usually begin to emerge from a typical DC model age of about 10^5 yr. The grain motion in a typical cold neutral medium (CNM) can help overcome the Coulomb repulsive barrier to enable effective accretion of cations onto positively charged grains. As a result, the grain motion greatly enhances the abundances of some gas-phase and surface species by factors up to 2-6 or more orders of magnitude in the CNM model. The grain motion effect in a typical molecular cloud (MC) is intermediate between that of the DC and CNM models, but with weaker strength. The grain motion is found to be important to consider in chemical simulations of typical interstellar medium.

20 pages, 10 figures and 2 tables

References in corpus (13)

• Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model
• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• A three-phase chemical model of hot cores: the formation of glycine
• Polycylcic Aromatic Hydrocarbons (PAH's) in dense cloud chemistry
• H3+ in Diffuse Interstellar Clouds: a Tracer for the Cosmic-Ray Ionization Rate
• A Unified Monte Carlo Treatment of Gas-Grain Chemistry for Large Reaction Networks. II. A Multiphase Gas-Surface-Layered Bulk Model
• Shattering and coagulation of dust grains in interstellar turbulence
• Gas-grain chemistry in cold interstellar cloud cores with a microscopic Monte Carlo approach to surface chemistry
• Cosmic ray induced ionisation of a molecular cloud shocked by the W28 supernova remnant
• Three-dimensional off-lattice Monte Carlo kinetics simulations of interstellar grain chemistry and ice structure
• A Unified Microscopic-Macroscopic Monte Carlo Simulation of Gas-Grain Chemistry in Cold Dense Interstellar Clouds
• A New and Simple Approach to Determine the Abundance of Hydrogen Molecules on Interstellar Ice Mantles
• Subsurface chemistry of mantles of interstellar dust grains in dark molecular cores

Cited by in corpus (8)

• Dust Motions in Magnetized Turbulence: Source of Chemical Complexity
• Interstellar chemical differentiation across grain sizes
• Three dimensional projection effects on chemistry in a Planck galactic cold clump
• GGCHEMPY: A pure Python-based gas-grain chemical code for efficient simulation of interstellar chemistry
• Magnetic field measurement from the Davis-Chandrasekhar-Fermi method employed with Atomic Alignment
• Chemical properties of two dense cores in a Planck Galactic Cold Clump G168.72-15.48
• Diagnostics of magnetohydrodynamic modes in the ISM through synchrotron polarization statistics
• Gas phase Elemental abundances in Molecular cloudS (GEMS). X. Observational effects of turbulence on the chemistry of molecular clouds