Chemical modeling of water deuteration in IRAS16293-2422

Abstract

IRAS 16293-2422 is a well studied low-mass protostar characterized by a strong level of deuterium fractionation. In the line of sight of the protostellar envelope, an additional absorption layer, rich in singly and doubly deuterated water has been discovered by a detailed multiline analysis of HDO. To model the chemistry in this source, the gas-grain chemical code Nautilus has been used with an extended deuterium network. For the protostellar envelope, we solve the chemical reaction network in infalling fluid parcels in a protostellar core model. For the foreground cloud, we explored several physical conditions (density, cosmic ionization rate, C/O ratio). The main results of the paper are that gas-phase abundances of H2O, HDO and D2O observed in the inner regions of IRAS16293-2422 are lower than those predicted by a 1D dynamical/chemical (hot corino) model in which the ices are fully evaporated. The abundance in the outer part of the envelope present chaotic profiles due to adsorption/evaporation competition, very different from the constant abundance assumed for the analysis of the observations. We also found that the large abundances of gas-phase H2O, HDO and D2O observed in the absorption layer are more likely explained by exothermic surface reactions rather than photodesorption processes.

20 pages, 15 figures. This version is slightly different from the published one because of language editor's modifications

References in corpus (7)

• 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
• Molecular Evolution and Star Formation: From Prestellar Cores to Protostellar Cores
• Photodesorption of water ice: a molecular dynamics study
• Formation of hydrogen peroxide and water from the reaction of cold hydrogen atoms with solid oxygen at 10K
• Warm water deuterium fractionation in IRAS 16293-2422 - The high-resolution ALMA and SMA view
• CH in absorption in IRAS16293-2422

Cited by in corpus (19)

• Binding energies: new values and impact on the efficiency of chemical desorption
• Water in star-forming regions (WISH): Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
• SOLIS II. Carbon-chain growth in the Solar-type protocluster OMC2-FIR4
• A new look at sulphur chemistry in hot cores and corinos
• The complex chemistry of outflow cavity walls exposed: the case of low-mass protostars
• The composition of the protosolar disk and the formation conditions for comets
• The ALMA-PILS survey: First detection of the unsaturated 3-carbon molecules Propenal (C${}_2$H${}_3$CHO) and Propylene (C${}_3$H${}_6$) towards IRAS 16293$-$2422 B
• Chemistry of TMC-1 with multiply deuterated species and spin chemistry of H2, H2+, H3+ and their isotopologues
• Methyl isocyanate CH3NCO: An important missing organic in current astrochemical networks
• Methyl cyanide (CH3CN) and propyne (CH3CCH) in the low mass protostar IRAS 16293-2422
• A study of singly deuterated cyclopropenylidene c-C3HD in protostar IRAS 16293-2422
• AB Aur, a Rosetta stone for studies of planet formation (II): H${}_2$S detection and sulfur budget
• H${}_2$S observations in young stellar disks in Taurus
• Chemical fractionation of deuterium in the protosolar nebula
• Carbon Isotope Fractionation of Complex Organic Molecules in Star-Forming Cores
• Constraints of the formation and abundances of methyl carbamate, a glycine isomer, in hot corinos
• Chemical Evolution of HC3N in Dense Molecular Clouds
• Physicochemical models: source-tailored or generic?
• About explosive delayed desorption from methane-doped argon matrices