UCLCHEM: A Gas-Grain Chemical Code

Abstract

We present a publicly available, open source version of the time dependent gas-grain chemical code UCLCHEM. UCLCHEM propagates the abundances of chemical species through a large network of chemical reactions in a variety of physical conditions. The model is described in detail along with its applications. As an example of possible uses, UCLCHEM is used to explore the effect of protostellar collapse on commonly observed molecules and to study the behaviour of molecules in C-type shocks. We find the collapse of a simple Bonnor-Ebert sphere successfully reproduces most of the behaviour of CO,CS and NH${}_3$ from cores observed by \citet{Tafalla2004} but cannot predict the behaviour of N${}_2$H${}^{+}$. In the C-shock application, we find that molecules can be categorized so that they can be useful observational tracers of shocks and their physical properties. Whilst many molecules are enhanced in shocked gas, we identify two groups of molecules in particular. A small number of molecules are enhanced by the sputtering of the ices as the shock propagates and then remain high in abundance throughout the shock. A second, larger set are also enhanced by sputtering but then are destroyed as the gas temperature rises. Through these applications the general applicability of UCLCHEM is demonstrated.

14 pages, Accepted for publication in AJ

References in corpus (12)

• SiO line emission from C-type shock waves : interstellar jets and outflows
• Parametrization of C-shocks. Evolution of the Sputtering of Grains
• Desorption From Interstellar Ices
• Phosphorus-bearing molecules in solar-type star forming regions: First PO detection
• H2S in the L1157-B1 Bow shock
• Shocks in dense clouds. IV. Effects of grain-grain processing on molecular line emission
• Water in Low-Mass Star-Forming Regions with Herschel: The Link Between Water Gas and Ice in Protostellar Envelopes
• The density structure of the L1157 molecular outflow
• Ethylene oxide and Acetaldehyde in hot cores
• Time-dependent simulations of steady C-type shocks
• Diagnosing shock temperature with NH${}_3$ and H${}_2$O profiles
• Molecular dark matter in galaxies

Cited by in corpus (9)

• Chemical modelling of complex organic molecules with peptide-like bonds in star-forming regions
• First detection of the pre-biotic molecule glycolonitrile (HOCH2CN) in the interstellar medium
• ALMA imaging of C2H emission in the disk of NGC1068
• Molecular transitions as probes of the physical conditions of extragalactic environments
• The L1157-B1 astrochemical laboratory: testing the origin of DCN
• The challenges of modelling microphysics: ambipolar diffusion, chemistry, and cosmic rays in MHD shocks
• Ambipolar diffusion and the molecular abundances in prestellar cores
• Nitrogen Fractionation in External Galaxies
• Investigating the Efficiency of Explosion Chemistry as a Source of Complex Organic Molecules in TMC-1